Comptometer, early form (wooden box), 72 keys numbered, plate on top of box engraved " Trade Comptometer mark, Patd. July 19th 1887, Oct 11th 1887, Jan 8th 1889, June 11th 1889, Nov 25th 1890, Dec 15th 1891, Felt & Tarrant Manufacturing Co., Chicago"
An early example of the Comptometer, with 72 numbered keys. The top of box has a plate engraved with varoius patents up to 1891. The Felt and Tarrant Comptometer was one of the first generation of mass-produced office calculators. It was extremely successful being able to multiply and subtract quickly and efficiently.