A circular slide rule from 1881, invented by M. Monsieur G. Charpentier, and rendered beautifully in brass and steel. It was robustly built for every day use. The back bears the maker’s name Morin, 15 Rue Dulong, Paris. Operating instructions are available at Operating Instructions for the Calculimètre (in French)1
1 From G. Martin of PhotoCalcul viewed 11 April 2014 (↑)
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