Baldwin Calculator
"In 1873, Baldwin applied for a patent for a machine which at all times had the capacity to add, subtract, multiply and divide with no resetting of the mechanism and with no form of conversion for any of the processes. While employed by a lumber company, Baldwin had been asked to repair a Thomas Machine, which is when he probably got the idea to build his own.

He replaced the Leibniz and Thomas cylinders with a single cylinder from whose periphery a variable number of teeth (1 through 9) protrude according to the motion of the setting lever. The levers project through slots at the front of the machine.

When the lever is set, corresponding numbers of teeth project from the wheel.
With a crank of the handle, the projecting teeth gear with a cogwheel, which activates a digit wheel, and the numbers corresponding to the projecting teeth appear in the register. Baldwin joined forces with Monroe in 1912 and formed the Monroe Calculator Company. A pioneer in electric adding machines since 1922, the firm is still in the business. "

David Weil, Computer Museum of America.

Source: Computer Museum of America.

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