A THOMAS DE COLMAR ARITHMOMETER, FRENCH, CA 1880-1900.

A brass calculating machine in mahogany case, "Arithmomètre" in-laid in contrasting wood to lid, ivory and brass operating handle, function change handle in ivory, with 16 number displays and 8 sliding indices. 23 x 7 x 3 ¾ in. in case. 

Hoyau, “Description d’une machine à calculer nommée Arithmomètre. . . ,” Bulletin de la Société d'Encouragement pour l’Industrie Nationale, 21, 1822, pp. 355–365

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Charles Xavier Thomas de Colmar (1785-1870) first patented the Arithmomètre in France in 1820, becoming the inventor of what was the first mechanical digital calculator that could be relied upon to be used in a commercial environment. The machine could directly perform additions & subtractions of two numbers as well as perform multiplications and divisions using the movable accumulator. The machines were manufactured from 1851 through 1915, and were a key tool in the paradigm shift from written to mechanical calculation.  While mechanically operated arithmetic machines were built after the designs of Pascal and Leibniz in the 17th century, machines of this kind were not used as a practical tool until de Colmar introduced his improved design in the 19th century.