Yet another Parisian (rue du Petit-Carreau 23) watchmaker (after Ernest-Narcisse Lobbé in 1855) invented an early keyboard adder in 1850s—Eugène Jacot des Combes (1825-1875) was a holder of two French patents for adding machines (machine à additionner) (Brevet №43781 from 1 February 1860, and Brevet №68027 from 11 July 1865). Jacot des Combes has also another patent from 1871 for apparatus for electrification of the air and ozone production.
The adding machine of Eugène Jacot des Combes is a column keyboard adder (while column adders can have two or more result digits, you can only add into the rightmost digit, and then generally only with the integers one through nine) with nine keys and a 3-positional result mechanism. It was one of the early keyboard adders, after the machines of White, Torchi, Schwilgué, Parmelee, the abovementioned Lobbé, Castle, Hill and Nutz.
The construction of the device (see the patent drawing below) seems to be simple and reliable, but nothing survived to our time about Eugène Jacot des Combes and his machines.