• 455 Martinson, Los Angeles
  • 8 (043) 567 - 89 - 30
  • support@email.com
  • 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

A man must have a hobby….


This non-commercial website was a novel 60th birthday present from Ros. But the site 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When the latest PC/tablet is out-of-date in 6 months it may come as a surprise that the Englishman in the image, the Rev.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. Being able to use one is still a licensing condition private and commercial pilots have to meet.

This site is a virtual “display cabinet” for my collection (as it gets uploaded) of slide rules and the odd mechanical calculating aid plus a “bookshelf” for my published articles - enjoy browsing.

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 introduction course with synchronised audio I digitalised. Afterwards try out some test calculations with Derek Ross’ online simulation of a Pickett N909-ES slide rule. If all this gets you thinking about starting your own collection then the UKSRC/OSBeginner’s Guide to Collecting Slide Rules” can be a great help.

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.

Latest additions


Slide Rules

Smallwood, I & D (John & Daniel), (NoName), Shoe folded size stick - metric, L, Other, wood/brass

Tech Papers

A Cheesy Tale

Gazette Issue 20

news - So far 1102 rules are loaded from my collection

05 October 2020


This batch includes many antique items. This is because for centuries governments have collected taxes on alcohol – “Nothing is certain but death and taxes”. Check out my eclectic variety of alcohol and ullage related calculating aids - including a subset just for beer!

14 September 2020


This year’s bumper and attractively priced edition of the UKSRC’s Gazette Issue 20 is now available. Ordering (payment via PayPal) could not be simpler via the UKSRC subscription ordering webpage (click on the imbedded link).

01 August 2020


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

24 May 2020


A milestone I expected to reach earlier. It takes ages to catalogue & capture conscientiously all the details. The upside is that I am learning a lot about my collection! The1000th entry was fittingly an unusual & extremely rare KLOOS disc for heavy-duty steel constructions

13 May 2020

STOP PRESS: new book

As a labour of love Otto van Poelje, an expert on ALRO, has published: The ALRO Catalogue. Dutch maker ALRO is famous for circular models where the lid doubles up as a desk stand. In 200+ pages every calculating disc, slide rule & slide chart ever made by ALRO is meticulously catalogued & photographed in a hardback book. Attractively priced at Euro 35 (excl. P&P) order your copy online here ...

19 April 2020


Rodger Shepherd sadly passed away peacefully at home on 16th April 2020. With Bob Otnes (1932-2019) Rodger co-founded the Oughtred Society (OS) in 1991. In 1992 he was the first OS Award winner and promoted publishing the Journal of the OS (JOS). He set high standards for his own research and others who subsequently published in the JOS. He translated Dieter von Jezierski’s ground-breaking 2000 book: “Slide Rules – A Journey Through Three Centuries”. Only last year he helped me make sense of a rare medical based slide rule. He will be missed.

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.

My wish list

Sought after slide rules still missing from the collection:
A.W. Faber-Castell4/92, 8/13, 8/14, 8/15, 8/168 & 51/88
Addiator GmbHOctadat
AHREND (Wed. J. Ahrend & Zoon)642T, 649, 651, 690, 696, 698, 699 & 701
Albert MartzCursor for pocket System Frank
ALRO (All-Round)Cobol Analyser, HaTex & Truck Tyres + any large desktop model
AWF (Ausschuss fuer Wirtschaftliche Fertigung)SR703, SR705-709, & SR754
Controller Calculator KG200 R
DARGUE Bros. Ltd / SimplonSub-Ivory SR-1 & SR-4 + Honduras SD10, WR-2A, WR-5 & WR-7
Engineering Instruments Inc.Either circular “vinylite” model
Fearns CalculatorsBarber Shop Harmony Calculator
FowlerNautical, Artillery, Kearns & Mackay
InglisFLASH RECKONER: Pricing, Photographic Exposure, Stock Exchange, Foreign Money, Paper Trades & Health Insurance
ITAB (Internationaler Tabellenverlag)Multicalor Flachheizkorper & Styropor-Vollwarmeschutz
IWA15489 Harmonik
Keuffel & Esser (K&E)4081-3 Braille version
L&C Hardtmuth / Classic10" Series III
Lawrence Engineering ServicesS-M (C.V. Ore) & Exposure (MIT)
LOGATF, T150, T300, O2, Terminator & Baumaan lighting
NestlerCursor/runner for 24b (100cm), RP 75, Kreisrechner & Disc-O-Lator
S.R.&S.E. (Slide Rule & Scale Eng. Co.)- any -
Systeem Matthijssen- any -
UniqueNorman, Perfectus, Dial & Junior