With the primary scales nearest to the rim this layout offered great precision (scale length 28cm) over the more popular 200 R that had the Trig scales nearest to the rim + codes H alongside central nameplate probably = country code for Holland

With the primary scales nearest to the rim this scale layout offered great precision (scale length 28cm) over the more popular 200 R that had the Trig scales nearest to the 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  

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

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) & 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

Rare example of circular Electro type ​

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

 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   

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 

Personally designed by company co-founder C.J. Dussel + BoB3 = possibly Beton (concrete) & part of alternative model numbering system + possible 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

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 

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 

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

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)

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 

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

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 

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 

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   

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  

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

 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

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

WeR2 is part of alternative model numbering system + WeR = possibly WeRktuigbouw (mechanical engineering) + suffix 5 possibly = version no. + possible forerunner to later (?) 100 R