• 455 Martinson, Los Angeles
  • 8 (043) 567 - 89 - 30
  • support@email.com
  • Hatters Gauge - for measuring the size of a hat but unusually calibrated in metric & imperial
  • Glovers Rule - for measuring the length of a glove
  • Unusual non-logarithmic squaring desktop QR 41 model by Dennert & Pape (D&P)
  • Colour combinations slide rule for Interior Designers
  • Professor Fuller’s Drum Calculator from 1878 - made by W.F. Stanley
  • Modern Kienzle wristwatch with slide rule bezel calculator
  • Ruxton Multi-Vider 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
  • Design for this Antenna Radar Beam Pattern Detection slide rule was classified during WWII by UK & US governments - made by Lawrence
  • Makeba Kombinator pencil & slide rule
  • Rare Carbic-made Fischer Calculator
  • Specialist slide rule for a national home cable radio broadcasting system offered in The Netherlands in the 1900s
  • Smallest drum (≈ 2.4m) made by LOGA

A man must have a hobby….


This non-commercial website was an amazing 60th birthday present from 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When the latest PC/tablet is out-of-date inside 6 months, it may come as a surprise that the Englishman in the image, the Rev. William Oughtred (1575-1660), invented a calculator around 1621 that would be in continual daily use for nigh on the next 400 years. My hobby is collecting and writing about this analogue calculating wonder - the SLIDE RULE. The analogue concept behind the slide rule 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 site is a virtual “display cabinet” for my collection (as it gets uploaded) of slide rules, slide charts and the odd mechanical calculating aid plus a “bookshelf” for my published articles - enjoy browsing.

My wish list

Sought after slide rules still missing from the collection:
A.W. Faber-Castell8/13, 8/14, 8/15 & 51/88
Addiator GmbHOctadat
AHREND (Wed. J. Ahrend & Zoon)642T, 649, 651, 690, 696, 698, 699 & 701
ALRO (All-Round)Beton, Cycloop, GoA, Ha, Piret, Nomographie, Van Leer & 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 – F. Riehle GmbH & Co KG15489 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 - 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!).

Anyone needing a “memory jogger” or is just intrigued how such analogue calculators of the past worked, the International Slide Rule Museum has a richly illustrated “How To Use The Slide Rule” teach yourself course or download a self-running 35mm “diafilm” Introduction Course with synchronised audio I digitalised. Afterwards try out some test calculations with Robert Wolf's online simulation of the classic Nestler 23R wooden slide rule. If all this gets you thinking about starting your own collection then the UKSRC/OSBeginner’s Guide to Collecting Slide Rules” is a must read.

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

news - So far 1273 items are loaded from my collection

01 January 2023


Wishing all the regular or new visitors to this website a happy & most importantly, a healthy 2023. Keep safe as COVID is still out there.

16 December 2022


Irenne Dennert (1927–2022) belonged to an important slide rule dynasty. She sadly & unexpectedly passed away on 3rd December. Her late husband, Hans Dennert, took over the family slide rule business Dennert & Pape - that later evolved in ARISTO. After Hans died Irene always generously shared the company archive with collectors. She will be missed.

02 November 2022


Rod Lovett’s facility listing all the slide rules of fourteen major makers has recently been expanded with seven partial image archives – click HERE to take a look.

03 September 2022


Issue 22 of the UKSRC Gazette is another bumper edition - 160 pages with 20 in-depth articles. As ever, this non-profit publication is excellent value for money & there is even a modestly priced PDF version for parts of the world were postage costs are prohibitive. Use this LINK to order your copy from the UKSRC Subscription & Gazettes webpage.

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 V 8.1 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 ….

11 December 2021


Rod Lovett’s latest facility makes the data compiled on Electro types over many years by Bob Adams easy to search. Use it to find all known specialist Electro and Electronic slide rules – try it out here …

27 October 2021


HEMMI with its sunburst logo is a highly respected Japanese maker of slide rules. The company has a rich history – operating from 1895-1975. HEMMI chose to make most of their models from bamboo with celluloid veneers. An understandable choice as bamboo was better suited to the humid conditions of their “home market”: Asia. They sold an impressive range of models - many with usual scale layouts. Click HERE to see the ones I have – including two models that each need 4 cursors to work!

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

Unknown, Sikkens Blind Color, Colour Blending, C, Duplex, card

Tech Papers

Keeping in Rhythm (updated IM2021 version)

JOS Vol. 31 No. 2