The history of the Felt Tarrant company

Dorr E. Felt began working on what would become the Comptometer in 1885, making the first working version in metal in 1886 (the 1885 model was made mostly of wood and spare parts), and began low volume production by hand in 1887. Felt went into partnership with Robert Tarrant to produce and refine the Comptometer over many years. Although rather common due to their relatively high production, the Comptometer is an historically significant machine, being the first successful multiple order key driven calculator. Felt's new carrying mechanism was complex, but it met the high speed requirement of a key driven calculator. The 8 column Comptometer could add faster than an accountant's brain, which was its key to success."

Mr. Dorr E.Felt invented the Comptometer 1885 in parralel with William S.Burroughs' developments. Both of them realized the same idea of an "Direct Keyboard" to perform addition immediately when the number is entered. Key of different digits can be pushed simultanieously without the use of a crank. The prototyp of his first model was built in a wooden macaroni box. D.E.Felt filed for a patent a year later than W.S.Burroughs, but got the patent in 1887, a year earlier. He founded the Felt & Tarrant Manufacturing Co. in Chicago, Illinois / USA in the same year. Over the years the machines got important improvements, an "Error Lock" against wrong handling e.g. The success of the Comptometer lasted till the 1970s, because skilled operators could speed-up book- keeping calculations, with the 10-Key adding and listing machines.
In 1961 the company merged with Victor to form Victor Comptometer Co.

For more details see the "Comptometer-HomePage" by Brooke W. Boering: