Listed 1st in catalogue from 1950 

With primary C/D scales nearest to outer rim this layout offered great precision (scale length 28cm) over more popular 200 R with Trig scales next to outer rim +  H alongside central nameplate probably = country code for Holland

With primary C/D scales nearest to outer rim this layout offered great precision (scale length 28cm) over more popular 200 R with Trig scales next to outer rim

Double cursor version of innovative but impractical single long-scale 6-spiral patented (CH265561) design + tables of conversion factors in lid - try out an online simulation created by Andries de Man

Single cursor version of Innovative but impractical single long-scale 6-spiral patented (CH265561) design  + tables of conversion factors in lid - try out an online simulation created by Andries de Man

​Table of conversion factors in lid  + Dutch retailer Bladergroen was an stationer from 1903 to 1980 when it was bought out & name changed to Berlage  - try out an online simulation created by Andries de Man

One of four metal box finishes (2 x metal & 2 painted) occasionally used

Code H alongside central nameplate probably = country code for Holland + table of conversion factors in lid

The use of two-tone paper discs is probably for better contrast/legibility - table of conversion factors in lid

One of four metal box finishes (2 x metal & 2 painted) occasionally used

One of four metal box finishes (2 x metal & 2 painted) occasionally used

Conversion chart (fractions/decimals) in lid

Reason for non-standard green/turquoise paper discs & for polished inside box is unknown

​Code H alongside central nameplate probably = country code for Holland + ​conversion chart (fractions/decimals) in lid

Because of a shortage of aluminium during WWII the metal boxes looked identical but for a short time were made of much heavier zinc + code H alongside central nameplate probably = country code for Holland + ​conversion chart (fractions/decimals) in lid

Unconventional 200 R with black heavy-duty metal back plate instead of desk stand - reminiscence of military model with just a back plate  

RL = Rietz Liniaal (ruler) + failed project to make white plastic linear model + 2 windows with hairline, two expansion slots & table of constants for metals on back - part of prototype batch of +/- 50  

RL = Rietz Liniaal (ruler) + later (CI scale no longer red) improved version with self-lubricating bearings + 2 windows with hairline, two expansion slots & table of constants for metals on back

Version without a P scale + table of conversion factors in lid - subsequently succeeded by 400 D

Version with added P scale + table of conversion factors in lid - subsequently succeeded by 400 D 

Successor to 300 D with many more gauge marks & CI replacing S&T & P in lid + table of conversion factors in lid ​- see also larger sibling

See also smaller sibling - conversion table of fractions also on back 

Ng = Normaal (normal) grafici (printers) ​+ scales on back convert mm into cicero’s/didot points

Nmmi = Normaal (normal) mm to inches + scales on back convert metric mm into imperial inches  

N = Normaal (normal) & is possibly successor to Ha.A2 but with smaller font to make more room for advertising + see also larger sibling 

N = Normaal (normal) + personally enhanced (lighter plastic outer baseplate & peripheral cursor hairlines) model of last ALRO Technical Director Han Wanders - see also smaller sibling 

N = Normaal (normal) & is possibly successor to Ha.A2 but with smaller font to make more room for advertising such as Belgium photographers Vergouts + tables of conversion factors from 1010 Commercial in lid

E = Electro & successor to ElA - both rare circular examples for this type 

H = High Frequency with special scales for inductance, capacitance & resonance + CJD monogram for company co-founder Dussel indicates an early model + scales in lid provide the dB figure for various power & voltage ratios - probably inspiration for the much later modern plastic Decibel PTT models  

De Muiderkring = the Dutch publishing arm of Amroh (American Radio House) specialising in radio technology + pictogram colour coding & table of resistances for condensers in lid - see also waistcoat sibling

De Muiderkring = the Dutch publishing arm of Amroh (American Radio House) - see also larger sibling 

Slide chart made for Dutch high street bank ABN (later merged with another bank to become ABN-AMRO) for calculating compound interest monthly payback on a 100 Dutch Gulden loan for rate of 11 to 15.5% (front) & 15.75 to 20% (back) for durations of 12 to 60 months  

 AL-RO model designation (never repeated) is a reference to the full company name + CJD monogram for company co-founder Dussel & earliest pre-production model from original Wildhoeflaan 21 address in The Hague + imperial conversion factors in lid - metal box maybe a replacement   

Slide Chart version 04a to promote ALRO's trade-marked process ALRODEREN or laminating paper in thin plastic & converting time across 7 times zones for 28 cities around the world

Ruler/protractor to promote/advertise ALRO company  

Ruler to promote/advertise ALRO company & their PVC products + special version for Amsterdam Efficiency Fair of 1986

Ruler to promote/advertise ALRO company & durability of their ALRODEREN process for German market

Model designation clearly pre-empting soon to be granted international patents + early pre-production & synonymous with Ha (= Handel -= Retail) + imperial conversion factors - try out an online simulation created by Andries de Man in lid 

Ruler made to promote ALRO's trade-marked process ALRODEREN or laminating paper in thin plastic + image of office facade in The Hague + horse-head company logo 

Ruler made to promote ALRO's trade-marked process ALRODEREN or laminating paper in thin plastic + coloured image of office facade in The Hague + horse-head company logo 

Ruler come sampler for to promote ALRO's trade-marked process ALRODEREN or laminating paper in thin plastic for their head office and only German subsidiary

Sampler to promote/advertise ALRO company & quality of their ALROPRINT (synonymous TM with ALROCARD) finish 

Slide chart made for Dutch research-driven global pharmaceutical company Boehringer Ingelheim for calculating  probability of myocardial infarction (heart attack) in patients with history of heart problems + AMI-RO = Acute Myocardial Infarction Rotterdam ​

Slide chart made for Swedish pharmaceutical company Astra that merged with British Zeneca Group in 1999 to form AstraZeneca for finding the anaesthetic pain control dosage for 31 different types of surgical operation  

Calculates the angular measurement in a spherical coordinate system or more the horizontal angle from a cardinal direction

​Slide chart for calculating optimum drilling of wells according to factors such as penetration rate, drill speed, hydraulic pressure drop, etc + B.I.P.M. = Bataafse Internationale Petroleum Maatschappij or forerunner of company now known as Shell

Slide chart for calculating needed & allowable maximum mud weight for a drilled & flowing well according to factors such as depth, pressure within drill pipe, annular surface pressure, etc + B.I.P.M. = Bataafse Internationale Petroleum Maatschappij or forerunner of company now known as Shell

Slide chart version 04e made for Belgium Bank Brussel Lambert (BBL) (Tradelink was the name of their network but bank later acquired by Dutch ING bank) for converting time across 7 times zones for 28 cities around the world

Slide chart made for 100% plant-based organic branded bioNorm proteins to convert Joules to Calories 

Personally designed by company co-founder C.J. Dussel + BoB3 = possibly Beton (concrete) & part of alternative model numbering system + forerunner to later Beton version but with additional 70 kg/cm2 scale & extensions for extra strong cement + scales in  lid are for calculating no. & size of reinforcement bars

Ruler made for German pharmaceutical company Boehringer Ingelheim & designed by F.A.M. Harms for analysing ECG printouts of cardiac Sinus Rhythms - read more ….  

Slide chart made for Dutch distillery Lucas Bols for mixing 30 different cocktails + tips for mixing drinks on back of slide

Slide Chart version 04a made for Dutch sales promotion company BOVI for converting time across 7 times zones for 28 cities around the world

Slide chart designed by Dutchman Wim Granneman in 1975 to calculate how to alter/change flowering/harvesting time of tulip bulbs + can also be used for other perennials & other countries with different seasons + issued by Dutch International Flower Bulb Centre

Slide chart for defunct Dutch subsidiary tool merchant of The Carborundum Company in the form of a wallet for determining machine settings - i.e. speed (rpm) for given diameters of types & coatings of grinding discs + speed table    

Slide chart made for defunct Dutch factory making printing forms of illustrations Clichéfabriek Maastricht for calculating % reduction/increase when for typesetting/engraving 

Chemical credence comes from over 140 chemical-related gauge marks + table of all atomic weights from 1948 in lid - see also online simulation by Andries de Man 

Slide chart for defunct Dutch subsidiary of USA machine tool builder Cincinnati Milacron with copyrighted design (1 moving ring) for calculating grinding parameters  + see also advanced sibling

Slide chart for defunct Dutch subsidiary of USA  machine tool builder Cincinnati Milacron with copyrighted design (2 independently moving rings) for calculating grinding parameters  + see also basic sibling

Slide chart/nomogram (n.b. not a slide rule) made for Dutch supplier of photographic darkroom products LiCi Colorstar for calibrating their early range of colour analysers in combination with a test print

Ruler (unusually fitted with a cursor) made for American pharmaceutical company Wyeth-Ayerst Laboratories (acquired by Pfzier in 2009) & registered brand name owner of Cordarone (drug for irregular heart beats) for analysing ECG printouts of cardiac Sinus Rhythms - read more ….  

Ruler (unusually with a cursor) probably prototype for American pharmaceutical company Wyeth-Ayerst Laboratories (acquired by Pfzier in 2009) & brand name owner of Cordarone (drug for irregular heart beats) for analysing ECG printouts of cardiac Sinus Rhythms + unlike sibling has plain back 

Slide chart DAST = DAtum (date) STandaard (standard) is a perpetual calendar for the years 1300 to 2499

Slide Chart version 04c made for defunct Euro-American card manufacturer Data Card (they later bought ALRO & in turn was acquired by conglomerate Entrust) for converting time across 7 times zones for 28 cities around the world

Slide Chart version 04d made for defunct Euro-American card manufacturer Data Card (they later bought ALRO & in turn was acquired by conglomerate Entrust) for converting time across 7 times zones for 28 cities around the world

Slide chart made for defunct Belgium photo engravers De Buck & Paulich for calculating % reduction/increase when for typesetting/engraving 

Slide Chart version 04a made for Dutch guild of artisan bakers De Echte Bakker for converting time across 7 times zones for 28 cities around the world

Slide chart made for Dutch construction company Gebr. de Kinkelder B.V. for calculating spread of workable days/month throughout the year - front for maximum of 200 working days/year & back for maximum of 191 (allowing for lost days due to high winds) working days/year  

Slide chart/ruler made for Dutch insurance company Delta Lloyd with unusual mirrored (anamorphosis) scale to measure thickness of framed glass by placing the bevelled top edge against the glass surface & reading off the thickness from the reflection

An architects ruler made for defunct Dutch construction company Demabao Systeembouw  

Slide chart made for defunct Dutch steel wholesaler Dikema en Chabot for calculating size & weight for a given length of steel bar with either a H or U profile 

Patented design (BE492292) by J.L. Brouhon from 1949 for wood merchants, wood sawmills, etc + tables of conversion factors from 1010 Commercial in lid + price included surcharge over other Ø 13cm models - see also online simulation by Andries de Man 

Slide chart for defunct Belgium cattle-feed supplier (factories in Deinze & Zolder) Dossche for calculating the estimated respective gestation time for pigs, sheep, cattle & horses

ElA = Electrotechniek (electrical engineering) forerunner to later 600 E & part of alternative model numbering system - both rare circular examples for this type 

Template made for defunct Dutch construction company Electra LAS COmbinatie Nederland (Elascon) for drawing profiles of metal roofing or cladding panels   

Slide chart for calculating power, efficiency & wiring of electric motors + EMF DORDT = nickname of defunct Dutch company Willem Smit & Co.‘s Electromotorenfabriek that produced large commercial electrical motors

Slide chart made for defunct Dutch wallpaper company Eerste Twentse Behang Industrie (ETBI) for calculating total price in Dutch Gulden for buying 7 to 12 rolls of wallpaper in price range of fl 1.20 to 5.85/roll  

Slide chart for defunct Finish company Finncell showing location, capacity & types of product produced at each of their 29 wood pulp/cellulose mills in Finland    

Slide rule/slide chart for calculating sound levels in dB for building facades - © 1983 design by ministerie  V en M = now defunct Dutch Ministerie van Volksgezondheid en Milieuhygiëne (Ministry of Health and Environmental Hygiene)

Slide chart made for Belgium manufacturer of photographic paper L. Gevaert & Cie (later became Belgium-German multinational company Agfa-Gevaert) for calculating how to optimally reproduce photographic images mechanically using an inked plate created from a photographic negative  

Slide chart made for defunct Dutch chemical & pharmaceutical company Gist-Brocades N.V. for calculating % of water to flour needed for 30 small or large pieces of dough for 13 different types of bread  

For air pressure & flow calculations + GRASSO-PERSLUCHT = Dutch company for industrial refrigeration equipment + table of constants/conversion factors & ALROPRINT on back 

Specially commissioned 50 Ng for Gravura N.V.  a printer & illustrator based in Dutch town of The Hague

Slide chart for converting heat transfer values in central heating systems + gti installatietechniek = Dutch plumbing company + ALROPRINT & © TRD/1977/10

Ha Tex = Handel (business) Textiel (textiles) for textile-based calculations with UK pre-decimal £sd currency & yards

Ha Tex = Handel (business) Textiel (textiles) for textile based calculations with UK pre-decimal £sd currency & yards + tables of conversion factors from 1010 Commercial in lid - see also online simulation by Andries de Man

Slide chart look-up table on back to help select most suitable heating pump for commercial use (e.g. greenhouses) from HA-ES “perfecta” range made by defunct Dutch company Meppeler Machinefabriek

Ha.A2 possibly part of alternative model numbering system & predecessor to 500 N AC-1.11 but with larger font & 4 pre-decimal & imperial conversion scales in lid + prefix Ha = possibly Handel (retail)

Slide chart for defunct Dutch car parts retailer HAVAM for torque settings + pressure & usage conversion tables  

Slide chart for defunct Dutch car parts retailer HAVAM for converting UK/USA imperial values to metric  

Ruler made for American multinational IT company Hewlett Packard (HP) & designed by F.A.M. Harms for analysing ECG printouts of cardiac Sinus Rhythms - read more ….  

Slide chart made for German chemicals/life-sciences company Hoechst AG (later became Sanofi Aventis) using a pair of dividers to measure size of elliptic skin sores (Laesiomat is Latin for hurting) & calculate area in mm² + adverts for branded skin salves on back 

Ruler Cor-V-Mat® incorporating nomograms made for German chemicals/life-sciences company Hoechst AG (later became Sanofi Aventis) & designed by Prof. Keuskamp for analysing ECG printouts of cardiac Sinus Rhythms - read more ….  

Slide chart made for defunct Dutch producer of oxygen & other gases Hoek Look for Amsterdam Infant Ventilator Machine designed by Prof. Keuskamp for calculating respiration flow rates & air/oxygen flow rates 

Ruler made for American International Business Machines (IBM) for working in Cicero, Pica & IBM typographic units with typewriters

Ruler made for American International Business Machines (IBM) for working in Points, Cicero, Pica & IBM typographic units in desk-top publishing 

Slide chart made for & © designed by KK/TRD consisting of consisting of 4 rings of energy saving tips ranked by low/medium/high investment levels for: (i)  heating systems (front) or (ii) lighting, energy & sanitation (back) 

Highly complex specialised layout of scales designed by Dr. A. Lips + facilitates 26 medical based calculations (metabolic-related on front & blood ph/gasses on  back) - read more … or try out  Andries de Man's two online simulations: (i) front & (ii) back 

Slide Chart version 04c made for Dutch airline KLM for converting time across 7 times zones for 28 cities around the world

Slide Chart made for Dutch airline KLM for calculating dimensional or volumetric weight (imperial or metric) based on a package's length, width & height using benchmark of either 7 cubic decimetres = 1 kg or 194 cubic inches = 1 Lb 

Load adjuster (possibly pre-production) made for Dutch airline KLM who had 1st fleet in Europe of American-made Convair 240 passenger planes - see also earlier prototype sibling  

Load adjuster prototype made for Dutch airline KLM who had 1st fleet in Europe of American-made Convair 240 passenger planes + table of conversion factors in lid - see also later (possibly pre-production) sibling

Slide chart made for frequent flyer/loyalty programme of Dutch airline KLM for converting time across 7 times zones for 117 KLM destinations around the world 

Slide chart made for Dutch airline KLM (old style logo) for converting imperial & US gallons to lbs, kg, etc for range & loading calculations - see also all-metal early version & prototype

All-metal silver coloured slide chart made for Dutch airline KLM (old style logo) converting imperial & US gallons to lbs, kg, etc for range & loading calculations - see final production model

Prototype slide chart made for Dutch airline KLM (old style logo) converting imperial & US gallons to lbs, kg, etc for range & loading calculations + strange reference to Portugal's Lisbon Portela airport- see final production model

Desktop version of smaller GoA with high-precision goniometric layout (double length Trig scales) by van Roon + specially commissioned flight computer for Dutch airline KLM for calculating course & wind correction 

Slide Chart for Dutch airline KLM for calculating the BMEP (Brake Mean Effective Pressure) for 3 series' of engine   

Slide chart for calculating steel forms needed to construct: (i) fixed & opening bridges & (ii) points & crossing for railways & tramways + KLOOS = F. Kloos en Zonen’s originally a Dutch ship builder that evolved into making all manner of heavy-duty steel constructions

Slide chart for calculating resistance in pipes (front) & pump capacity needed (back) + KNM Begemann = defunct Dutch company Koninklijke Nederlandsche Machinefabriek v/h E.H. Begemann manufacturing pumps & steel constructions + table of resistance values on back ​

Slide chart with © design for a consortium of 4 Dutch regional newspapers so customers could calculate advertising costs of a chosen layout/size (once-off or repeated) in Dutch Gulden + cm & Cicero scales on back    

Slide chart with © design for a consortium of 4 Dutch regional newspapers so customers could calculate advertising costs for a chosen layout/size (once-off or repeated) in Dutch Gulden - cm & Cicero scales on back + possible prototype as lacking the cut-outs to top edge for slide adjustment found on sibling version in white

Unusual battery-driven light exposure meter (with built-in micro measuring cell) made for for Dutch supplier of photographic darkroom products LiCi Colorstar according to a copyrighted design by Phlip van Meeuwen (GFK) 

Slide chart eating guide made for Dutch subsidiary of American pharmaceutical company Eli Lilly & jointly issued with the Dutch Diabetes Society for finding kcal, Kh(g) & MK (= meal code) values for many types of food & drink 

Made for Dutch Army with scales calibrated in NATO Milliradian (Mils) ​for angular measurement + pouch with belt clip shows it was intended for use in field of action 

Made for Dutch Army with scales calibrated in NATO Milliradian (Mils) ​for angular measurement but being metal cased version was for army barracks or classroom/study 

Made foreign armies with scales calibrated in NATO Milliradian (Mils) ​for angular measurement but being metal cased version was for army barracks or classroom/study 

Slide chart made for founding company Organaon for pregnant mother’s in early stages of pregnancy for planning when to donate urine to help other couples with fertility problems + Moeders voor Moeders = Dutch pharmaceutical organisation that extracts hCG hormone from the urine to create fertility medicines + see also larger version

Slide chart for pregnant mother’s in early stages of pregnancy for planning when to donate urine to help other couples with fertility problems + Moeders voor Moeders = Dutch pharmaceutical organisation that extracts hCG hormone from the urine to create fertility medicines + see also pocket versions

Slide chart for pregnant mother’s in early stages of pregnancy for planning when to donate urine to help other couples with fertility problems + Moeders voor Moeders = Dutch pharmaceutical organiation that extracts hCG hormone from the urine to create fertility medicines + see also larger version 

Slide chart for pregnant mother’s in early stages of pregnancy for planning when to donate urine to help other couples with fertility problems + Moeders voor Moeders = Dutch pharmaceutical organisation that extracts hCG hormone from the urine to create fertility medicines + see also larger version

Slide Chart version 04d made for American biopharmaceutical company MSD (Co-Renitec is brand name for a high blood pressure treatment) for converting time across 7 times zones for 28 cities around the world

Slide rule/slide chart for predicting traffic sound levels according to several parameters such as type of road, type of vehicle, etc according to design by H.J. van Zuylen + Nationale Verkersakademie Tilburg = defunct Dutch technical school in Tilburg for educating traffic specialists

Slide rule/slide chart for predicting traffic sound levels according to several parameters such as type of road, type of vehicle, etc according to design by H.J. van Zuylen + Nationale Verkersakademie Tilburg = defunct Dutch technical school in Tilburg for educating traffic specialists

Slide chart made for defunct Dutch digital printers Nauta &  Haagen (later Kampert-Nauta) for calculating % reduction/increase when for typesetting/engraving 

Slide chart version 04b made for Dutch consultancy consortium Nederlandse Export Combinatie (NEC) for converting time across 7 times zones for 28 cities around the world 

Ned. Octr. Aangevr. = Dutch patent applied for so possibly an early pre-production model with CJD monogram for company co-founder Dussel + imperial conversion factors in lid - sadly metal box & patent nameplate are replacements   

​Slide chart for calculating the significance between two independent statistical samples + NIPO = Nederlands Instituut voor Publieke Opinie (Dutch institute for public opinion) + table of conversion factors for reliability on inner slide

Slide chart made for unnamed company or organisation (but where form. 5007 03-90 60.06 has some meaning) for calculating duration in hours (maximum two weeks) between two daytime timeslots in a calendar week

Unusual slide rule/slide chart/nomograms (2 x Ø 7½cm discs) made for unnamed company or organisation (but Ka6 is a single-seater glider built by Alexander Schleicher GmbH & Co in Germany) for use as simple flight computer & for wind speed conversion + flying check-lists on back 

Protractor/ruler without any branding but classic 180⁰ scale is paired with NATO military favoured alternative: MILS   

Slide chart made for Dutch founded healthcare company Nutricia that later became part of French conglomerate Danone for calculating, according to a baby's weight, number & size daily doses for 6 baby food/nutrition products   

​Slide chart with © design Dept. of Transport & Public Works of The Netherlands for predicting the probable outcome of an oil spill based on spread, drift, mass balance, evaporation, dispersion & emulsification

Nomogram made for global healthcare company Organon showing contraception efficacy of 2 estragon & 9 other oral contraceptives for differing parts of menstrual cycle  

Slide chart made for Dutch electronic multinational Philips for determining Acceptable Quality Level % (AQL) according American military defence standard (MIL-STD-105-D) showing maximum acceptable number of defects for a given batch size with either Single or Double samples for: Normal (N), Tightened (T) & Reduced (R)

​Slide chart for Dutch electronic multinational Philips for calculating dB decibel ratios & converting them into various current, voltage & power ratios + 1 of 3 versions

Slide chart made for Dutch electronic multinational Philips with © design for their P300 bookkeeping minicomputer showing available functions according memory sectors A to S

Slide chart/nomogram for ELA (Electro-Acoustiek) division of Dutch electronic multinational Philips for calculating dB decibel ratios & converting them into various current, voltage & power ratios + 1 of 3 versions

Slide chart/nomogram for ELA (Electro-Acoustiek) division of Dutch electronic multinational Philips for calculating dB decibel ratios & converting them into various current, voltage & power ratios + earliest of 3 versions  

Slide chart made for Dutch electronic multinational Philips for calculating foetal size & age from crow-rump length (CRL) or foetus length from top of head to bottom of torso & biparietal scull diameter (BPD) ultrasound results

Slide chart for Dutch electronic multinational Philips to  check specificatiions for OC series of tansistors 

Slide Chart (later version) made for Dutch electronic multinational Philips for showing 8-pin layout (a=anode, f=filament, g=grid, h= heated, k=cathode & i.c.= internally connected) of Miniwatt range of valves + see earlier sibling  

Slide chart (early version) made for Dutch electronic multinational Philips for showing 8-pin layout (a=anode, f=filament, g=grid, h= heated, k=cathode & i.c.= internally connected) of Miniwatt range of valves + see also later sibling  

Nomogram made for Dutch electronic multinational Philips for designing 6 different carbon film resistors with 3 different resistor values 

Larger versions made for PTT 

Slide chart made for Dutch electronic multinational Philips for step-by-step set up/troubleshooting schematics & settings of XG 7100/XG 7104 TV control unit

Specially commissioned by UK-based A.C. Wickman Ltd. + designed by Nestor Piret for wire drawing while working for defunct Dutch company Van Thiel's Draadindustrie + paper table in lid for Wichman Wimet Die sizes 4/10 to 36 showing equivalent sizes in circular Mils & mm according to 6 wire gauge standards  - try out an online simulation created by Andries de Man

Slide chart designed as planisphere by Dutchman R. Walrecht to calculate star positions & star signs at latitude 52º North & longitude 5º East for given date & time + just 1000 made but later versions made by PlantijnCasparie 

Slide chart made for Dutch branded pregnancy test Planosec showing the pregnancy cycle in weeks/months from 1st day of last menstruation to expected date of birth    

Slide Chart made for Dutch lightbulb maker Pope (later taken over by Dutch electronic multinational Philips) for showing the 8-pin layout (a=anode, f=filament, g=grid, h= heated, k=cathode & i.c.= internally connected) of Philips valves + see later Philips version

Ruler made for defunct Dutch medical electronics company Portanje Elektronika & designed by F.A.M. Harms for analysing ECG printouts of cardiac Sinus Rhythms  - read more ….  

Slide Chart version 04c made for Dutch paint company Primap Coatings for converting time across 7 times zones for 28 cities around the world

PTT = Posterijen, Telegrafie en Telefonie or old Dutch post, telegraph & phone company & ​NL NR 04 - 2220 = ordering no. + see smaller sibling

PTT = Posterijen, Telegrafie en Telefonie or old Dutch post, telegraph & phone company & ​NL NR 04 = ordering no. + see larger sibling

Slide rule/slide chart for calculating radioactive doses & intensities from a 1978 patented design (US4117315) from C.G.F. Amy & K.K. Keimpema+ issued as 4/8/1075/76346 by PTT = Posterijen, Telegrafie en Telefonie or old Dutch post, telegraph & phone company + see also large demonstration sibling

Slide rule/slide chart for calculating radioactive doses & intensities from a 1978 patented design (US4117315) from C.G.F. Amy & K.K. Keimpema+ issued as 4/8/1075/76346 by PTT = Posterijen, Telegrafie en Telefonie or old Dutch post, telegraph & phone company + see also smaller but not small sibling

Slide chart made for medicine trade name Questran for calculating number of daily doses of cholestyramine to reduce cholesterol - these days drug largely replaced by statins 

Slide rule/slide chart made for Dutch military personnel (NATO NSN no. 6665-17-055-1115) to calculate the effects & fall out directly after a nuclear explosion

Slide chart with unusual construction & colour-coding for for choosing resistors & capacitors with appropriate values & tolerances 

Adapted 200 R with gauge marks as pay-out odds for 6 popular types of bets possible on the numbers part of a French style roulette table - reputedly conceived by Capt. Hans Feierabend  read more … 

Slide chart made for defunct Belgium agrochemical company N.V. Schering S.A. for calculating the the appropriate use of pesticides when growing beetroot  

Slide Chart made for Shell for normal & heavy-duty metal bolts per ASA & BS tables in inches & mm & according the Shell's Group 81 MESC (Material and Equipment Standards and Code) catalogue specification

Shell © clock (klok) design for calculating in 4 standard units viscosity of various oils at different temperatures - try out an online simulation created by Andries de Man

Rare load adjuster for an American helicopter + prototype possibly made for aviation branch of Dutch Navy (Marine Luchtvaartdienst - MLD) who nicknamed it Jezebel 

Slide rule/slide chart for predicting overall railway trackside noise level in dB(A) according to several parameters e.g. noise screen, type & frequency of trains, average speed, etc - ALROPRINT 922130

One of a pair of rules, without slides but with erasable cursors faces for hand-drawn pencil hairlines, made for the Dutch Army – the laminated (Alroderen™) paper tables & model # are ex-Army

Two of a pair of rules, without slides but with erasable cursors faces for hand-drawn pencil hairlines, made for the Dutch Army – the laminated (Alroderen™) paper tables & model # are ex-Army

​Slide chart converting viscosity values between various standardised units + SYRES = Dutch company (still operating) specialising in commercial coatings & resins for buildings, boats, cars, etc 

Specially commissioned 10 R for T.K.F. = Twentsche Kabelfabriek (Twentsche Cable Factory) was originally a cable manufacturer based in Dutch town Haaksbergen but is now a leading supplier of connectivity solutions

Slide chart (in various colours) for designing cast meral pipe flanges & fittings according to ANSI standard B16 + Tebodin is an abbreviation for “Nederlandsch Technisch Bureau voor Ontwikkeling der Industrie” (Dutch Technical Bureau for Development of Industry) founded by Frederik van Iterson in1945  

Slide chart (in various colours) for designing cast metal pipe flanges & fittings according to ANSI standard B16 + Tebodin is an abbreviation for “Nederlandsch Technisch Bureau voor Ontwikkeling der Industrie” (Dutch Technical Bureau for Development of Industry) founded by Frederik van Iterson in1945  

Slide chart made for registered brand name Teronac (generic name for slimming drug no longer normally available) to calculate an individuals Body Mass Index (BMI) based just on metric height & weight

Ruler made for Dutch Organistie Voor Toegepast Natuurwetenschappelijk Onderzoek (TNO or Organisation for Applied Scientific Research) Instituut voor Bouwmaterialen en Bouwconstructies (IBBC or Institute for Building Materials & Construction) to measure cracks in walls   

 CJD monogram of company co-founder Dussel suggest an early model for determining large/heavy goods vehicle (HGV) tyre sizes + 3rd party Table of Truck Tyre Pressures in lid

Slide chart possible made as prototype to show 8-pin layout (a=anode, f=filament, g=grid, h= heated, k=cathode & i.c.= internally connected) of Miniwatt range of valves + see later Philips production version

Slide chart made for Germany company Valvo (when still part of electronic multinational Philips) for designing different low-frequency transistors

Slide chart made for 40th anniversary of Dutch training organisation Stitching VAM (these days called Innovam & for cars) for calculating annual financial yield in Dutch Gulden for shops selling 100 to 700 bicycles/year  

Specially commissioned 10 R for Van Kranenburg a now defunct heavy machinery company based in Dutch city of Rotterdam

Slide chart for looking-up DIN & NEN standard sizes for nuts & bolts according to ISO & Whitworth standards + VERCOMBI refers to a joint purchasing company of the day for Dutch makers of screws & bolts Nedschroef & EWES  + see also sibling version

Slide chart/slide rule by Dutch supplier of farming machinery VICON (VIssers Construction Nieuw-Vennep) for calculating fertilizer distribution + see also sibling version

Slide chart with © design by Dutch supplier of farming machinery VICON (VIssers Construction Nieuw-Vennep) for calculating fertilizer distribution + see also sibling version

Template/ruler (opaque) made for defunct Dutch IT company Volmac (later became part of Capgemini) for documenting with symbols processes & tasks which need to occur in a particular order

Template/ruler (opaque) made for defunct Dutch IT company Volmac (later became part of Capgemini) for documenting with symbols processes & tasks which need to occur in a particular order

Slide chart for looking-up DIN & NEN standard sizes for nuts & bolts according to Metric & Whitworth standards + VvS refers to a joint purchasing company of the day for Dutch maker of screws & bolts Verkoopkantoor voor Schroefbouten + see also sibling version

WeM is part of alternative model numbering system + WeM = possibly Werktuig- en Machinebouw (mechanical engineering/machine industry) + possible forerunner to later (?) 200 R

WeR = possibly WeRktuigbouw (mechanical engineering) & part of alternative model numbering system + forerunner to later 100 R - later WeR2's included a  version no. although only discernible difference on a later sibling was scale annotations in red   

 WeR = possibly WeRktuigbouw (mechanical engineering) & part of alternative model numbering system + forerunner to later 100 R - model suffix 5 is possibly version no. although only discernible difference to earlier sibling is scale annotations in red 

Nomogram made for defunct Dutch company Zyma-Nederland to help doctors by showing expected kidney renal function/performance levels for creatinine clearance & serum creatinine based on a patient's age & weight (n.b. underlying formulas now considered obsolete)