• 455 Martinson, Los Angeles
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  • Smallwood Folding Shoe Sizing Stick in metric for French shoe sizes 10-48 in increments of a Paris point (⅔ cm)
  • Lawrence MIT Antenna slide rule for radar antenna performance was classified during WWII by UK & US governments
  • ALRO-made ruler unusually with a cursor for analysing ECG printouts of the cardiac Sinus Rhythms
  • Hatters Gauge - for measuring the size of a hat but unusually calibrated in metric & imperial
  • Glovers Rule - for measuring the length of a glove in imperial inches
  • Unusual non-logarithmic QR 41 military model by Dennert & Pape (D&P) for training anti-aircraft gunners
  • Colour combinations slide rule made by German WH-Wohnen for Interior Designers
  • Professor Fuller’s Drum Calculator from 1878 - made by W.F. Stanley
  • Modern wristwatch with slide rule bezel calculator made by German maker Kienzle
  • Ruxton made Multi-Vider combined drop-lead pencil & slide rule
  • Rare Otis King Model N for Retail & Monetary with white scales (422 & 424) on a black background
  • Darnley’s Rotable Lightning Calculator/Pencil Case calculating aid
  • Makeba made Kombinator combination pencil & slide rule
  • Rare Carbic-made Fischer Calculator slide rule
  • Specialist slide rule for a national home cable radio broadcasting system offered in The Netherlands from 1930 to1970
  • Smallest drum (≈ 2.4m) made by renowned Swiss maker LOGA

A man must have a hobby….


This non-commercial website was an amazing 60th birthday present from my soulmate Ros. But the website name is thanks to another family member - our daughter Siân. When asked as a teenager what I did, she often told her friends: “My Dad? Oh, he collects expensive sticks of wood!”

When the latest PC/tablet is out-of-date inside 6 months, it may come as a surprise that the Rev. William Oughtred (1575-1660) invented his Circles of Proportion calculator around 1621. This analogue principle was in continual use for nigh on the next 400 years. My hobby is collecting and writing about this analogue calculating wonder - the SLIDE RULE. Over the years the concept was successfully adopted and adapted by many trades and professions. Remarkably being able to use such an elegant analogue instrument from a bygone age is still a licensing condition for all private and commercial pilots.

This website is a virtual “display cabinet” for my collection (as I uploaded it) of slide rules, slide charts and mechanical calculating aids plus a virtual “bookshelf” for my published articles - enjoy browsing.

My wish list

Sought after models still missing from the collection:
A.W. Faber-Castell1/38, 8/13, 8/14, 8/15 & 51/88
Addiator GmbHOctadat
AHREND (Wed. J. Ahrend & Zoon)642T, 649, 651, 690, 696, 698, 699 & 701
ALRO (All-Round)101, 10 RL, Beton, Cycloop, GoA, Ha.C/P/Q/V, Ha TEX, Piret, Philips Calendar, Nomographie, Van Leer, Vonderlingenplaat & WeR4
AWF (Ausschuss fuer Wirtschaftliche Fertigung)SR703, SR705-709, & SR754
Controller Calculator200 R
DARGUE Bros. Ltd. / SimplonSub-Ivory SR-1 & SR-4 + Honduras SD10, WR-2A, WR-5 & WR-7
Fearns CalculatorsBarber Shop Harmony Calculator
FowlerNautical, Artillery, Kearns & Mackay
ITAB (Internationaler Tabellenverlag)Multicalor Flachheizkorper & Styropor-Vollwarmeschutz
IWA (Ingenieurbuero fuer wirtschaftliches Arbeiten)15489 Harmonik
Johann Faber180/080, 180/082, 9203, 9204 & 9204
Keuffel & Esser (K&E)4081-3 Braille version
KOSMOSBook: "De Rekenliniaal" - 11th & 12th Editions
L&C Hardtmuth / Classic10" Series III
Lawrence Engineering ServicesS-M (C.V. Ore) & Exposure (MIT)
LOGA Calculator A.G.TF, T150, T300, O2 Calculator, 30 TxC & 75 Terminator
Logomat Rechengeräte1300/1303
NestlerRP 75, Kreisrechner & Disc-O-Lator
S.R.&S.E. (Slide Rule & Scale Eng. Co.)- any -
Systeem Matthijssen- any -
UniqueJunior, Study 500/700/900 & J180/181/182

The history of the slide rule - how it all began ....


To learn more about the history of this calculating wonder check out the “Slide Rule History” by the Oughtred Society (OS) or my 2-page summary (in Dutch).

Those needing a “memory jogger” or is intrigued how such bygone analogue calculators worked, the International Slide Rule Museum (ISRM) offers an illustrated teach yourself course: “How To Use The Slide Rule”. Alternatively download the self-running 35mm “slide show” Training Programme with synchronised audio commentary I digitalised. Afterwards try out some test calculations using Robert Wolf's online simulation of the classic Nestler 23R wooden slide rule. If this gets you thinking about starting your own collection, then the UKSRC/OSBeginner’s Guide to Collecting Slide Rules” is a must read.

For educators looking for maths related inspiration and teaching aids/material then you need to look no further than Nicola Marras’ slide rule inspired website. But if you are just looking for reference works/published books on slide rules try one of these inventories: List 1 or List 2.

news - So far 1395 items are loaded from my collection

05 September 2023


Engineers Krusse & Larsen developed a dividing machine that enabled Danish company DIWA to produce a range of slide rules. Early models were mostly Rietz types & made from mahogany. Later they moved to all plastic & sold other types & specialist models. Their heyday was the 1950s & 1960s. The business closed in 1979. 

Check out my collection of DIWA’s here ...

26 March 2023


It was time for a spring clean. Some information on this website needed refreshing and/or updating. 

The changes were not major but I also took the opportunity to made the “look & feel” more consistent.

05 February 2023


Tom Martin, one of the UKSRC's longest serving members, sadly passed away in hospital at the beginning of January. Tom was an international expert on all things Gauging, Brewing and Hydrometry. He was a warm-hearted gentle giant who would always freely share his knowledge with fellow collectors. Tom will be sorely missed.

02 November 2022


Rod Lovett’s facility listing the slide rule models of 14 major makers has recently been expanded with 7 new image archives – click HERE to take a look.

26 July 2022


Thanks to Jose G. Fernández collectors can now download free-of-charge English & Spanish translations of Rechenschieber im Wandel der Zeit - a book published in 2009 by Guus Craenen. It charts the development and evolution of the slide rule from 1787 to 1905. Click HERE to go to the download webpage.

05 March 2022


After going digital 15 months ago and over 1,000 free downloads it was time for an update. Edition V8.1 of Peter Holland’s definitive book (in English and German) on every slide rule made by A.W. Faber and A.W. Faber-Castell is now free to download from here ….

01 August 2020


Did you know a special model exists for each house of Hogwarts School of Witchcraft & Wizardry? Depending on your Gryffindor, Ravenclaw, Hufflepuff or Slytherin affiliations select your Harry Potter inspired sorcerous slide rule simulation from Robert Wolf’s website ...

01 October 2019


Generically a slide rule can solve complex calculations but CANNOT do simple arithmetic. A rare and unusual exception is the newest addition to the collection - a System Korte slide rule that CAN add and subtract!

09 May 2018

Amazing Digital Slide Rule

Ace Hoffman has developed an awesome simulation of a linear, round, concentric and drum slide rule. From Ace's Homepage download a function-rich version for your phone, tablet or desktop.

02 February 2017


Lawrence made the only known slide rule considered so vital to the WWII effort that the UK & US governments had it classified - based on research from MIT it calculated radar antenna beam patterns, beam width, gain, etc.

Latest additions


Slide Rules

Griffin & Co. Ltd. (Charles), Horse Power Computer for Steam Engines, Speed poly-disc (3), C, Other, cardboard

Tech Papers

A Calculated Gamble

Gazette Issue 23