Wikipedia
Arithmaurel
[[Image:Dessin d'un Arithmaurel.png|thumb|right|upright=1.5|
]] First patented in France by Timoleon Maurel, in 1842, the Arithmaurel was a mechanical calculator that had a very intuitive user interface, especially for multiplying and dividing numbers because the result was displayed as soon as the operands were entered. It received a gold medal at the French national show in Paris in 1849. Unfortunately its complexity and the fragility of its design prevented it from being manufactured.
Its name came from the concatenation of Arithmometer, the machine that inspired its design and of Maurel, the name of its inventor. The heart of the machine uses one Leibniz stepped cylinder driven by a set of differential gears.