Monroe High-Speed Adding Calculator - c1920

This is a rare Monroe High-Speed Adding Calculator circa 1920. Prior to the introduction of electronic calculators, this was your desktop computer. The operation of the Adding Calculator is derived from Gottfried Leibniz's original stepped drum mechanism, and is capable of performing multiplication and division. Multiplicands are entered on the main Comptometer-style keypad, rather than being entered on a separate ten-key keypad. No plastic here, it's made of steel and brass. Enter the numbers and turn the crank clockwise to add, and counter clockwise to subtract. It multiplies and divides too! The finish shows the expected signs of wear and use after 100 years, but the mechanism works flawlessly