Monopol Calculating Machine

This lever-set non-printing pinwheel duplex calculating machine has six levers that are rotated forward to set digits from 0 to 9. The pinwheels that carry out arithmetic operations are not beneath the levers but in a separate row of wheels in back of them. The machine has a lever at the right bottom front and a crank for shifting the carriage at the center front. The set-up mechanism has two sliding decimal markers.

Behind this mechanism is a large carriage that has a row of 12 result dials at the front, a row of 14 result dials behind this, and a revolution register with seven dials behind these. These dials each have 20 digits around the edge. Alternate digits are for problems in addition and multiplication and for problems in subtraction and division. The windows showing the dials may be set to show either sets of digits. The revolution register has a carry mechanism. Both result registers have sliding decimal markers. Wheels used to set up numbers are between the dials of the result registers. The operating crank is on the left. Two rods are on both the right and the left side of the carriage.

The machine has an extremely heavy steel frame and mechanism. The outside is covered with a layer of silver-colored metal stamped with a small foliate pattern. A mark on the front reads: MONOPOL. A mark on the left side of the carriage reads: A.M. A mark on the right side of the carriage reads: S.D. The serial number, 367, is on a crosspiece visible only when the carriage is lifted.

According to Martin, this was the first pinwheel calculating machine with tens-carry in the revolution register. Monopol machines reportedly were manufactured between 1894 and 1914.

Reference:

E. Martin, The Calculating Machines (Die Rechenmaschinen), trans. P. A. Kidwell and M. R. Williams, Cambridge: MIT Press, 1992, p. 125.

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