Links

A compilation of interesting reference sites and search facilities I regularly visit and use. Please let me know if you think I have overlooked any interesting or important.
Site owner/purpose	Description/reason for my interest
Arithmomuseum site	Prime reference part of a larger site covering the history of Hungarian-made slide rules such as Gamma, Calderoni, Rotor, etc.
Ace Hoffman’s site	Digital Slide Rules: free download for your phone, tablet or desktop of a powerful simulation with linear, round, concentric and drum slide rules
Andries de Man’s site	Prime reference site for many documents recording the History of Calculators
Antonio Pérez-Prados site (ES)	Prime reference site for more than 1000 ancient calculating aids - from abacuses to calculus books and everything in between
ARC site (ES)	Spanish language collectors group: Amigos de las Reglas de Cálculo
Archive of Collections search	Oughtred Society: facility developed by Rod Lovett to search outstanding archived collections & image galleries of OS members
Art Simon’s site	Prime reference site for everything to do with wristwatch slide rules (resurrected via Wayback Machine from 2013)
Barbara Haeberlin’s site (DE)	RECHNERLEXICON: a superb information-rich site encyclopedia of all aspects of Mechanical Computing
Blue Book search	Herman’s Archive: Herman van Herwijnen’s (1929–2004) legacy online catalogue of more than 5000 slide rules & calculating aids
Bob Wolfson’s site	Eclectic mix of calculators & slide rules (including some unusual models) each with a brief synopsis
British Industrial History site	Grace's Guide: reference site for post-industrial revolution information & reference sources on companies, products & people
Chemical search	Chemical Slide Rule Archive: a Rod Lovett facility for specialist chemical slide rules
Chris Sangwin’s site	Many readable articles explaining the history & background to slide rules & other mathematical instruments (resurrected via Wayback Machine from 2016)
Christian Hamann’s site	Handy listing of the potted history of many popular slide rule brands & makers
Clark McCoys’ site	Prime reference site for everything to do with American slide rule maker Keuffel & Esser (catalogues, manuals, etc)
Colin Tombeur’s site	Prime reference site for pre WW2 German-made A.W. Faber & Faber-Castell slide rules + own uniquely designed specialised slide rules (e.g. for juggling)
Coopers’ Tool Museum site	Prime reference part of a larger site for cask or bottle making & gauging wooden tools
Daniel Toussaint’s † site (F)	Prime reference site for antique calculating aids & specifically for French-made GRAPHOPLEX slide rules
Dating & Timeline search	International Slide Rule Museum's (ISRM) handy “one-stop” section with dating guide & development timeline for slide rules from various makers
Dave Hoyer’s site	Prime reference site for everything to do with slide rule precision, accuracy & significant digits
David Green’s site	Prime reference site for everything to do with planimeters & early computers
David M Riches’ site	Prime reference site for mechanical instruments & many slide rule makers but especially Blundell Harling
Denis Roegel’s site	LOCOMAT: prime reference site for everything to do with important historical mathematical tables
Dick Lyon’s site	Prime reference site for everything to do with slide rule maker Carbic & their Otis King calculator (history, models, types, dating, etc)
Douglas K. Stevenson’s list	Prime reference site for estimating issuing year of a German Patent (DRGM) or German Registered (DRP) Design (resurrected via Wayback Machine from 2016)
Electro/Electronic search	Electronic Archive: a Rod Lovett developed facility based on Bob Adams' compilation of specialist electro or electronic types of slide rule
Fabrizio Brentini’s site (DE)	Prime reference site/catalogue for slide rules from German maker A.W. Faber or Faber-Castell (resurrected via Wayback Machine from 2024)
Friedrich Diestelkamp’s site (DE)	ADDIATOR: reference site for everything to do with the “big world of small calculators” or slide adders
George Keane’s site	Prime reference site for the history & slide rules of American maker Festus Mfg. Co. & its successor The Acu-Rule Mfg. Co.
Gerhard Wenzel’s site	Prime reference site for everything to do with pocket calculating devices
Giovanni Breda’s site	Cosmopolitan diverse collection of slide rules & mechanical calculators
Glossary search	International Slide Rule Museum: an extensive alphabetical list of slide rule related terms & definitions
Gonzalo Martin’s site (FR)	PhotoCalcul: prime reference site for makers GRAPHOPLEX, Lenoir, Tavernier-Gravet & others lesser-known French makers
Greg Scott’s site	Greg’s Slide Rules: handy site for downloading digital copies of a wide a range of slide rule manuals
Herbert Schneemann & Walter Szrek’s (DE)	Prime reference site for everything to do with calculating machines
Hubert van Dongen’s site	Archived collection covering every aspect of slide rules from the German maker A.W. Faber or Faber-Castell
Hyperbolic search	Hyperbolic Archive: a Rod Lovett facility based on Bill Robinson’s compilation of specialist vector type of slide rules with Sh & Th scales
Instrument Makers search	Webster Signature Database: compiled by Roderick S. & Marjorie K. Webster about people attributed to scientific instruments (via Wayback Machine from 2021)
Jaap Scherphuis	Prime reference site for everything to do with mechanical calculators
Jeffrey Donovan’s site	Prime reference site for everything to do with Sikes' Hydrometers (resurrected via Wayback Machine from 2014)
Jim Cerny’s list	Table of slide rules & slide charts for calculating time needed to do machining operations, often with use of a lathe
John Oakhill’s site	Prime reference site for UK slide rule maker Thornton/P.I.C. (resurrected via Wayback Machine from 2024)
John Vossepoel’s site	Planimetrica: reference site for many published catalogues of scientific instruments
John Wolff’s site	Web Museum: prime reference site for anything to do with calculating machines (mechanical & electronic)
Jorge Fabregas Zazza’s † site (ES)	ZAZAA: prime reference site many makers but especially everything to to with German maker A.W. Faber & Faber-Castell
Jörn Lütjens’s site (DE)	JOM: online museum for abacus', slide rules & German made ARISTO electronic pocket calculators (resurrected via Wayback Machine from 2024)
JOS literature search	OS Journal Literature Search: Rod Lovett’s facility to search for PDF versions of articles published in the Journal of the Oughtred Society
Jose G. Fernández (ES)	Extensive alphabetical list/catalogue (part of ARC site) of all known Spanish-made slide rules & slide charts
Kees Nagtegaal’s site	Mechanical Calculator: prime reference site for non-electric mechanical calculating devices
Kimura Satoru’s site (JP)	Prime reference site for Japanese-made slide rules
Klaus Kühn’s site (DE)	COLLECTANEA de LOGARITHMIS: prime reference site for everything to do with Logarithms & their spiritual father John Napier
KRING (NL)	Dutch language collectors group: Dutch Circle for Historical Calculating Instruments
Landesmuesum site (DE)	TECHNOSEUM: prime reference site for slide rules & office equipment from German maker NESTLER
Literature search	Slide Rule Article Search: Rod Lovett’s unmissable facility for literary references & articles published in the JOS, Gazette, Skid Stick or IM proceedings
Long-Scale search	Long Scale Slide Rule Archive: a Rod Lovett facility based on the late Ed Chamberlain’s early work but reorganised by yours truly of specialist long-scale type of slide rule
MAAS Museum seach	Powerhouse Collection: Australian Museum of Applied Arts and Sciences’ online collection includes eclectic mix of well catalogued slide rule memorabilia
Major Makers search	Slide Rules of the Major Makers: a Rod Lovett facility for catalogue listings & image galleries of fourteen major slide rule makers - from ALRO to UNIQUE
Martin Brenner’s site	Prime reference site for everything to do with Pilot Balloon slide rules (via Wayback Machine from 2025)
Martin Šesték’s site (CZ)	Prime reference site for everything to do with slide rule maker LOGAREX and other Czechoslovakian makers
Mike Konshak’s site	International Slide Rule Museum: a superb information-rich site for everything & anything calculator orientated
Mike Syphers	Following the Rules: comprehensive website uniquely showing the history of slide rules & featuring lots of reference information for collectors
Nathan Zeldes’ site	History of Computing: information packed site featuring many interesting slide rules & other historical computing artefacts
National Museum of American History	Prime reference site for a wide-range & eclectic mix of understandably mainly American slide rules
Nicola Marras site	Calcolatoria Educational Solutions: prime reference site for calculating teaching aids & material to inspire the youth of today
NSN/NIIN search	National Stock Number/National Item Identification Number search: the 9 or 13-digit numbers often found on slide rules commissioned by governmental MoD’s, etc
Oak Ridge Associated Universities site	Museum of Radiation & Radioactivity: reference site for Radiation and Nuclear Fallout slide rules & slide charts
OS	America based world-wide collectors group: Oughtred Society
Patent search	ESPACENET: worldwide search facility of the European Patent Office
Paul Ross’ site (dealer)	The Slide Rule Trading Co.: has the most complete HEMMI catalogue and POST cross-reference table (now hosted by ISRM website)
Rarities Gallery OS	Rarities Gallery: a collection hosted by the Oughtred Society of rare items from the member collections
Rarities Gallery UKSRC	Rarities Gallery: a collection hosted by the UK Slide Rule Circle of rare items from the member collections
Rick Furr’s site	Prime reference site for everything to do with the Liechtenstein-made CURTA mechanical calculator
Robert Wolf’s site	Prime site for replica simulations of many well-known SR models from different makers & including House of Hogwarts! (via Wayback Machine from 2024)
Rod Lovett’s site	Prime reference site for German maker ARISTO but also the "got to" site for a multitude of essential slide rule related tools & search facilities
Ron Manley’s site	Archived multi-faceted site for all aspects of slide rule collecting
RST (DE)	German language collectors group: Rechenschieber-Sammler Treffen
Scale list	ISRM’s reference list & graphical depiction of 75 different standard logarithmic scales by Andrew Nikitin
Stadia search	Stadia Slide Rule Archive: a Rod Lovett facility for specialist surveying/tachymetric type of slide rules
Stefan Heimann’s site (DE)	Prime reference site for everything to do with slide rules for Civil Engineering (via Wayback Machine from 2023)
Stephan Weiss’ site (DE)	Prime reference site for the History of Mechanical Calculation with Numbers
Steve Seale’s site	Steve’s Slide Rules: impressive mixture of specialist models & books - particularly handy is the grouping of specialist models into trade/profession based categories
UK Registered Design search	The National Archives: dating guide for “diamond/lozenge shaped” registration marks & catalogue of registered designs from 1839 to 1991
UK Trademark search	The National Archives: catalogue of recognisable symbols of a specific manufacturer or brand registered as a trademark from 1876 to 1938
UKSRC	English language collectors group: UK Slide Rule Circle
University of Greifswald site (DE)	Extensive online collection of digital & analogue calculating instruments - including many slide rules (via Wayback Machine from 2021)
Walter Shawlee II † site (dealer) (CA)	The Slide Rule Universe: hosts an information rich archive alongside items for sale
Wayne Harrison’s site	One collector's interesting take on what constitutes as unusual slide rules
Websites search	Net Search: Rod Lovett’s unmissable facility for searching known slide rule & calculating related websites
Wilifired Denz (DE)	Prime reference site for everything to do with mechanical calculators
WWII British broad arrow list	UK MoD: list of dates that correspond to letter codes that can appear alongside the broad arrow "crows feet" pheon often found on slide rules of the WWII era