Amusing little steampunk calculator. You enter a number using the sliders around the outside, and then turn the crank. The input number is added to whatever number is in the result register on the top. Pulling the handle upwards and turning does subtraction instead of addition. The ring is used to clear the result register and/or the crank count. The band around the top of the body can be rotated, to pre-multiply the input number (and crank count) by powers of ten.
(Am I looking a gift horse in the mouth by saying that you should be able to add by turning the handle clockwise and subtract by turning it counter-clock?)