Dorr E. Felt patents the comptometer
11th October 1887
Dorr Eugene Felt (March 18, 1862 – August 7, 1930) was an American industrialist who invented the comptometer, a mechanical calculator.
The comptometer is an historically significant machine, because it was the first commercially successful key-driven calculator.
Felt gained a patent for his device, US 371496, on 11th October 1887.
In the same year, Felt went into partnership with Robert Tarrant to form the Felt & Tarrant Manufacturing Company, which manufactured many different versions of the comptometer over the following years.