THE CALCULIMETRE CHARPENTIER, French, c.1900, signed “Calculimetre, G. Charpentier, Brevete S.G.D.G.” The 2-3/8″ (6 cm) diameter calculator is made of nickel silver and brass, divided with logarithmic, square root, tangent and sine scales on both sides, the suspension affixed to twin cursors and a frontal circular scale. A milled edge allows one to rotate the main body against this suspension assembly. Condition is fine, the surface somewhat cleaned and scratched. The Charpentier calculator, a fine pocket slide rule, is analogous to the Mannheim design but with circular scales. It was covered by a French patent, and by a British one in 1882, and was listed in American Keuffel & Esser catalogues from 1895 up to 1927, and in Dietzgen catalogues (see Otnes, 1991). Despite this, surviving examples are relatively uncommon; here we are able to offer a good French one, complete with photocopies of instructions and of the original French patent papers.
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David and Yola Coffeen both have enjoyed academic careers, as planetary astronomer and as linguist/educator. But since 1982 (yes, 1982!) they have been full-time dealers in early scientific and medical instruments, under the name Tesseract. Selling primarily by catalogue (over 100 issued so far) they also have a web presence at www.etesseract.com, and can be contacted at [email protected]