Links

A selection of sites I regularly visit or use for reference. Please let me know if you think I have overlooked any interesting/important sites.
Site owner/purpose	Description/reason for my interest
Arithmomuseum	Prime reference sites for Hungarian-made slide rules - e.g. Gamma, Calderoni, Rotor, etc.
Ace Hoffman’s simulations	Amazing Digital Slide Rule: download for your phone, tablet or desktop an an awesome free simulation of a linear, round, concentric or drum slide rule
Andries de Man’s site	Prime reference site for many documents recording the History of Calculators
Antonio Pérez-Prados (ES)	Prime reference site for old calculating aids used for education in schools
ARC (ES)	Spanish “Amigos de las Reglas de Cálculo” collectors group
Art Simon	Prime reference site for everything to do with slide rule wristwatches (via Wayback Machine from 2013)
Barbara Haeberlin’s site (D)	RECHNERLEXICON: a superb information-rich site & largest encyclopedia of Mechanical Computing
Bill Robinson’s list	Prime reference site for everything to do with slide rules with Hyperbolic scales - his work resulted in the Hyperbolic Slide Rule Archive
Bob Adam’s site	Collector friend from “Down-Under” with a special interest in Electro and Hyperbolic slide rules - his work resulted in the Electronic Archive
Bob Wolfson	Eclectic mix of slide rules including some unusual models
Books & Manuals search	ISRM library/archive search: over 500 downloadable slide rule related books, manuals, instruction sheets, etc
British Industrial History	Grace's Guide: prime reference site for post industrial revolution information & reference sources on companies, products and people
Catalogue search	Herman’s Archive: Herman van Herwijnen’s (1929–2004) legacy online “Blue Book” catalogue of more than 5000 slide rules & calculating aids
Chris Sangwin’s site (archived)	Many readable articles explaining the history and background to slide rules & other mathematical instruments (via Wayback Machine from 2016)
Clark McCoys’ site	Prime reference site for everything to do with slide rule maker Keuffel & Esser (catalogues/manuals/etc)
Colin Tombeur’s site	Juggler/collector with special focus on pre WW2 Faber/Faber-Castell slide rules + own design specialised slide rules (e.g. for juggling)
Coopers’ Tool Museum	Prime reference site for vintage wooden rules
Daniel Toussaint’s † site (F)	Prime reference site for antique calculating aids & specifically for slide rule maker GRAPHOPLEX
Dating & Timeline guide	ISRM’s handy “one-stop” aid for dating slide rules from various makers
Dave Hoyer’s site	Prime reference site for everything to do with slide rule precision, accuracy and significant digits
David Green’s site	Prime reference site for everything to do with Planimeters
David M Riches’ site	Prime reference site for slide rule maker Blundell Harling + superb collection of mathematical instruments/slide rules.
David Walker’s site	Novel take on accuracy “Typical Slide Rules Under the Microscope” + follow-on piece "The quest for precision and accuracy"
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/Otis King calculator (history, models, types, dating, etc)
Douglas K. Stevenson	DRGM & DRP dates: shortcut for estimating issuing year of a German patent or German Registered Design (via Wayback Machine from 2016)
Electro types search	Electronic Archive: Rod Lovett facility based on the work by Bob Adams over many years to search for all specialist Electro & Electronic types
Encyclopaedia of Mechanical Calculating	Rechnerlexikon: rich source of articles/images and patent related information on every possible aspect of mechanical calculating
Encyclopedia search	ISRM Glossary search: extensive glossary of slide rule related terms and definitions
Fabrizio Brentini’s site (D)	Prime reference site for almost anything related to maker A.W. Faber/A.W. Faber-Castell
Friedrich Diestelkamp’s site	Prime reference site for everything to do with the “big world of small calculators” (Addiatiors)
George Keane’s site	Prime reference site for the history of slide rule maker Festus Mfg. Co. and 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
Gonzalo Martin’s site (F)	PhotoCalcul: Prime site for makers GRAPHOPLEX, Lenoir, Tavernier-Gravet & others lesser-known French makers (history/dating/catalogues)
Greg Scott’s site	Greg’s Slide Rules: handy site for a range of downloadable manuals
Herbert Schneemann & Walter Szrek’s (D)	Prime reference site for everything to do with calculating machines
Hubert van Dongen’s site	Archive site predominantly for maker A.W. Faber/A.W. Faber-Castell
Hyperbolic scales search	Hyperbolic Slide Rule Archive: Rod Lovett search facility using Bill Robinson’s earlier work identifying SR's with Sh & Th vector scales
IMAGE search	Handy website that allows a reverse search on an existing image or the URL of an existing image
Instrument Makers search	Webster Signature Database: compiled by Roderick S. & Marjorie K. Webster holding information about people who made/signed scientific instruments (via Wayback Machine from 2021)
ISRG search	International Slide Rule Group: online discussion forum for slide rules and associated mechanical calculating instruments
Jeffrey Donovan’s site (archived)	Prime reference site for everything to do with the Sikes' Hydrometer (via Wayback Machine from 2014)
Jim Cerny’s list	Prime reference list for slide rules & slide charts for machining operations, often with the use of a lathe
John Oakhill’s site	Prime reference site for slide rule maker Thornton/P.I.C.
John Vossepoel	Planimetrica: prime reference site for catalogues of scientific instruments
John Wolff’s	Web Museum: prime reference site for everything to do with calculating machines (mechanical & electronic)
Jorge Fabregas’ site (ES)	ZAZAA: Prime reference site (history/images/catalogues/manuals/patents/cursor evolution/etc) for maker A.W. Faber/A.W. Faber-Castell
Jörn Lütjens Online Museum	JOM: features (I) Abacus Museum, (ii) Slide Rule Museum and (iii) ARISTO electronic pocket calculators - all based on Jörn’s collection
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
José Carlos’ site (ES)	Prime reference site for slide rule maker ARISTO
Kees Nagtegaal’s site	Mechanical Calculator: great site for non-electric mechanical calculating devices.
Kimura Satoru’s site (J)	Prime reference site for Japanese made slide rules
Klaus Kühn’s site (D)	COLLECTANEA de LOGARITHMIS: prime reference site for everything to do with Logarithms and their spiritual father: John Napier
KRING (NL)	Dutch Circle for Historical Calculating Instruments
Landesmuesum site (D)	TECHNOSEUM: Prime reference site for slide rules from maker NESTLER
Literature search	Slide Rule Article Search: Rod Lovett’s unmissable facility to search for literary sources/references published in the JOS, Gazette, Skid Stick or IM proceedings
Long-Scale types search	Long Scale Slide Rule Archive: Rod Lovett facility based on the late Ed Chamberlain’s earlier work (reorganised by yours truly) to search for all types with a long-scale
Louis van Wijk’s site	One of two reference sites for Radiation and Nuclear Fallout slide rules
MAAS Museum	MAAS: Australian Museum of Applied Arts and Sciences’ online eclectic collection of well catalogued slide rules
Major Makers search	Slide Rules of Major Makers: Rod Lovett facility listing all the slide rules of fourteen major makers - from ALRO to UNIQUE
Makers/brand history	Christian Hamann’s handy potted history of many popular slide rule brands/makers
Martin Brenner’s site	Prime reference site for everything to do with Pilot Balloon slide rules
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	ISRM: International Slide Rule Museum - a superb information-rich site for everything and anything calculator orientated
Nathan Zeldes’ site	History of Computing: information packed site featuring many interesting slide rules & other historical computing artefacts
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	One of two reference sites for Radiation and Nuclear Fallout slide rules
OS	American Oughtred Society
Patent search	ESPACENET: worldwide search facility of the European Patent Office
Paul Ross’ site (dealer)	The Slide Rule Trading Co.: specialises in selling spare parts but importantly also has the most complete HEMMI catalogue and POST cross-reference table
Price & scarcity check	eBay Slide Rule Search: Rod Lovett’s facility for checking the USD prices & scarcity of eBay slide rule auction postings dating back to November 1999
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 downloadable replica simulations of many well-known models from different makers & including a model for each House of Hogwarts!
Rod Lovett’s site	Prime reference site for maker ARISTO and Herman’s Archive but also legendary site for Rod’s own collection + an essential set of search facilities and much more
Ron Manley’s site	Legendary multi-faceted site for all aspects of slide rule collecting
RST (D)	German Slide Rule Collectors Group but their website doubles as a digital archive for many interesting articles, meeting reports, etc
Scale Finder	ISRM’s reference list/graphical depiction of Andrew Nikitin's 75 different slide rule scales
Stephan Heimann’s site (D under construction)	Prime reference site for everything to do with Civil Engineering slide rules
Stephan Weiss’ site (D)	Prime reference site for the History of Mechanical Calculation with Numbers
Steve Searle’s site (under development)	Steve’s Slide Rules: impressive mixture of specialist models & books - particularly handy is the grouping of specialist models into trade/profession based categories
The National Museum of American History	Prime reference site for a wide-range & eclectic mix of mainly American slide rules
UK Registered Design search	The National Archives: dating guide for “diamond/lozenge shaped” registration marks & catalogue of registered designs 1839-1991
UK Trade Mark search	The National Archives: catalogue of recognisable symbols of a specific manufacturer or brand registered as a trade mark 1876-1938
UKSRC	UK Slide Rule Circle
University of Greifswald site (D)	Extensive online collection of digital & analogue calculating instruments - including many slide rules
Virtual Museum of Slide Rules	Prime reference site for everything to do with Hungarian makers such as Gamma
Walter Shawlee II site (dealer)	SPHERE: The Slide Rule Universe - has a great archive alongside items for sale
Wayne Harrison’s site	One collector's interesting take on what constitutes unusual slide rules
Websites search	Net Search: Rod Lovett’s unmissable facility for searching known slide rule & calculating related websites
WWII British broad arrow letter codes	UK MoD: list of dates that correspond to letter codes that can appear alongside broad arrow "crows feet" pheon