Illustration from a Felt & Tarrant advertisement that makes a comparison between the calculating devices of prehistoric peoples and the modern Comptometer. Dorr E. Felt began working on the precursor to the Comptometer in 1885, 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. A historically significant machine, the Comptometer is was the first succesful multiple order key driven calculator and one of the first generation of mas-produced office calculators.
© Science Museum / Science & Society Picture Library