Comptometer
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The comptometer was the first commercially successful key-driven mechanical calculator, patented in the United States by Dorr Felt in 1887.
Prototype of the first all-electronic desktop calculator marketed by Sumlock Comptometer Ltd of the UK
The macaroni box (1885)
Model A (1905)
Model J (1930s)
Dorr Felt
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Dorr Eugene Felt was an American inventor and industrialist who was known for having invented the Comptometer, an early computing device, and the Comptograph, the first printing adding machine. The Fe
Comptometer
…The comptometer was the first commercially successful key-driven mechanical calculator, patented in the United States by Dorr Felt in 1887. It was a key-driven calculator that was extremely fast because each key adds or subtracts its value to the accumulator as soon as it is pressed…
Dorr E Felt Portrait
Felt Summer Mansion
Felt's grave at Rosehill Cemetery