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  • Ruxton Multi-Vider drop-lead pencil & slide rule
  • Rare Otis King Model K - white scales on black background
  • Pocket Hexadecimal Slide Adder for Computer Programmers
  • Post 1824 Dring & Fage Alcohol Gauging Rule
  • Darnley’s Rotable Lightning Calculator/Pencil Case
  • Lawrence Antenna (classified by UK & US during WWII) for Radar Beam Pattern Detection
  • Makeba Kombinator pencil & slide rule
  • Rare Carbic-made Fischer Calculator
  • For Calculating Strength of Liquids in Twaddells !!
  • PTT rule for Cable Radio (Signal Loss/dB)
  • Smallest drum (≈ 2.4m) made by LOGA

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You searched for: ALRO
ModelTypeMaterialCommentsThumbnail
100 R (AC-1.04b) Rietz - early metal/paper

Scale layout gives higher precision than sibling 200 R (AC-1.05b)

ALRO 100 R (AC-1.04b) Rietz - early
1010 Commercial (AC-1.18) Business long-scale metal/paper

Innovative but impractical single long-scale 6-spiral patented (CH265561) design & a pain to calculate with + tables of conversion factors in lid

ALRO 1010 Commercial (AC-1.18) Business long-scale
200 R (AC-1.05a) Rietz metal/paper

​Table of conversion factors in lid - try out here the online simulation created by Andries de Man

ALRO 200 R (AC-1.05a) Rietz
200 R (AC-1.05a) Rietz - H - early metal/paper

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

ALRO 200 R (AC-1.05a) Rietz - H - early
200 R (AC-1.05a) Rietz - two-tone metal/paper

Reason for two-tone paper unknown - table of conversion factors in lid

ALRO 200 R (AC-1.05a) Rietz two-tone
200 R (AC-1.05b) Rietz - early metal/paper

Conversion chart (fractions/decimals) in lid

ALRO 200 R (AC-1.05b) Rietz - early
200 R (AC-1.05b) Rietz - green metal/paper

Reason for green paper, shiny aluminium box & no scales in lid is unknown

ALRO 200 R (AC-1.05b) Rietz - green
200 R (AC-1.05b) Rietz - H metal/paper

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

ALRO 200 R (AC-1.05b) Rietz - H
200 R (AC-1.05b) Rietz - heavy metal/paper

Heavier zinc replaced aluminium as base metal during WWII years + ​conversion chart (fractions/decimals) in lid

ALRO 200 R (AC-1.05b) Rietz - heavy
200 RL (AC-1.49) Rietz plastic

​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

ALRO 200 RL Rietz
300 D (AC-1.08a) Darmstadt metal/paper

Predecessor to 400 D AC-1.09a​ + table of conversion factors in lid

ALRO 300 D (AC-1.08a) Darmstadt
300 D (AC-1.08b) Darmstadt metal/paper

Predecessor to 400 D AC-1.09a ​but with P scale

ALRO 300 D (AC-1.08b) Darmstadt
400 D (AC-1.09) Darmstadt metal/paper

Successor to original 300 D (AC-1.08a) but with S&T replaced by CI scale & many more gauge marks + table of conversion factors in lid ​

ALRO 400 D (AC-1.09) Darmstadt
50 Ng (AC-1.47a) Pocket Basic Printing plastic/metal

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

ALRO 50 Ng (AC-1.47a) Pocket Basic Printing
500 N (AC-1.11) Basic metal/paper

N = Normaal (normal) & is possibly successor to Ha.A2 AC-1.12 but with smaller font to make more room for advertising such as Belgium photographers Vergouts + tables of conversion factors from 1010 Commercial AC-1.18 in lid

ALRO 500 N (AC-1.11) Basic
600 E (AC-1.19) Electro metal/paper

Rare example of Electro type in circular form ​

ALRO 600 E (AC-1.19) Electro
AMI-RO-METER Boehringer Ingelheim (AC-4.01) Medical plastic

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

ALRO AMI-RO-METER Boehringer Ingelheim (AC-4.01) Medical
BoB3 C.J. Dussel Reinforced Concrete metal/paper

BoB3 uses an alternative model numbering system + is comparable to AC-1.22 but with extra 70 kg/cm2 scale (extra strong sort of cement) & other extensions + BoB prefix = possibly Beton (concrete)

ALRO BoB3 C.J. Dussel Reinforced Concrete
De Muiderkring (AC-1.27) 746 Radio metal/paper

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 + pocket AC-1.44 sibling

ALRO De Muiderkring (AC-1.27) 746 Radio
De Muiderkring (AC-1.44) Pocket Radio plastic/metal

De Muiderkring = the Dutch publishing arm of Amroh (American Radio House) + larger AC-1.27 sibling + versions for PTT & Philips Telecoms also made

ALRO De Muiderkring (AC-1.44) Pocket Radio
EMF DORDT (AC-3.10) Electro plastic

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

ALRO EMF DORDT (AC-3.10) Electro
GRASSO-PERSLUCHT (AC-2.22) Refrigerant/Conversion plastic

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

ALRO GRASSO-PERSLUCHT (AC-2.22) Refrigerant/Conversion
gti installatietechniek (AC-2.10) Central Heating plastic

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

ALRO gti installatietechniek (AC-2.10) Central Heating
Ha.A2 (AC-1.12) Basic Retail metal/paper

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)

ALRO Ha.A2 (AC-1.12) Basic Retail
HYDRAULIC RELATIONS IN DRILLING B.I.P.M. (AC-2.01) Petroleum plastic

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

ALRO HYDRAULIC RELATIONS IN DRILLING B.I.P.M. (AC-2.01) Petroleum
KLOOS (AC-1.30) Steel Constructions plastic/paper

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

ALRO KLOOS (AC-1.30) Steel Constructions
KNM BEGEMANN (AC-2.27) Pipe Flow plastic

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 ​

ALRO KNM BEGEMANN (AC-2.27) Pipe Flow
MILITAIRE REKENSCHIJF (AC-1.32) Military Artillery Range Finding metal/paper

Non-standard scales calibrated for NATO Milliradian (Mils) ​for angular measurement

ALRO MILITAIRE REKENSCHIJF (AC-1.32) Military Artillery Range Finding
MOEDERS VOOR MOEDERS (AC-4.11) Medical plastic

Slide chart for pregnant mother’s in the early stages of pregnancy so they can plan when to donate urine to help other couples with fertility problems + Moeders voor Moeders = Dutch pharmaceutical company that extracts hCG hormone from the urine to create fertility medicines

ALRO MOEDERS VOOR MOEDERS (AC-4.11) Medical
MUD WEIGHT - FLOWING WELL B.I.P.M. (AC-2.02) Petroleum plastic

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

ALRO MUD WEIGHT - FLOWING WELL B.I.P.M. (AC-2.02) Petroleum
NIPO INDICATOR (AC-7.09) Statistics plastic

​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

ALRO NIPO INDICATOR (AC-7.09) Statistics
Oil Spill (AC-7.04) Petroleum plastic

​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

ALRO Oil Spill (AC-7.06) Petroleum
PHILIPS AUDIO COMMUNICATIIONS (AC-3.02) Electro/Conversion plastic

​Slide chart for calculating dB decibel ratios & converting them into various current, voltage & power ratios

ALRO PHILIPS AUDIO COMMUNICATIIONS (AC-3.02) Electro/Conversion
PHILIPS TELECOMMUNICATION DECIBEL (AC-1.44) Pocket Radio plastic/metal

Versions for PTT & Muiderkring also made

ALRO PHILIPS TELECOMMUNICATION DECIBEL (AC-1.44) Pocket Radio
PLANISFEER (AC-6.05) Desktop Astronomy plastic/carboard

Slide chart designed as planisphere by Dutchman R. Walrecht to calculate star positions & star signs in Northern Hemisphere (52º North Lat. & 5º East Long.) for given date & time + just 1000 made

ALRO PLANISFEER (AC-6.05) Desktop Astronomy
PTT DECIBEL (AC-1.42) Radio plastic/metal

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

ALRO PTT DECIBEL (AC-1.42) Radio
RADIOLOGISCHE REKENSCHIJF (AC-7.01) Pocket Military Radiation plastic

For Dutch military personnel (NATO NSN no. 6665-17-055-1115) to calculate the effects & fall out directly after a nuclear explosion

ALRO RADIOLOGISCHE REKENSCHIJF (AC-7.01) Pocket Military Radiation
Radiologsche rekenschijf PTT (AC-7.02a) Radiation plastic

Part 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

ALRO Radiologsche rekenschijf PTT (AC-7.02a) Radiation
rekenschuif spoorweglawaai (AC-7.04) Transport plastic

For predicting railway trackside noise level in dB(A) according to several parameters e.g. noise screen, type & frequency of trains, average speed, etc - ALROPRINT 922130

ALRO rekenschuif spoorweglawaai (AC-7.04) Transport
SHELL VISCOKLOK (AC-1.40) Petroleum plastic/metal

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

ALRO SHELL VISCOKLOK (AC-1.40) Petroleum
SYNRES (AC-2.23) Conversion plastic

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

ALRO SYNRES (AC-2.23) Conversion
T.K.F. HAAKSBERGEN (AC-1.45c) 10 R Pocket Rietz plastic/metal

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

ALRO T.K.F. HAAKSBERGEN (AC-1.45c) 10 R Pocket Rietz
Verkeerslawaai (AC-7.05) Transport - green & black plastic

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

ALRO Verkeerslawaai (AC-7.05) Transport
WeR2 5 (AC-1.07b) Rietz metal/paper

WeR2 possibly part of alternative model numbering system + WeR = possibly WeRktuigbouw (mechanical engineering) + suffix 5 possibly = version no. + layout comparable to 100 R AC-1.04b

ALRO WeR2 5 (AC-1.07b) Rietz