This crank driven machine multiplies quickly and easily. You set one number in the keys, then crank the big crank forward one turn to add one and back to subtract. For each digit, you crank forward that many times and then turn the handle on the front a half-turn to move the carriage over one position. Then you do the next digit, and so on. The answer shows up in the bottom dials.
Division works like multiplication in reverse, and the answer shows up in the top dials.
The little crank resets the counters. Monroe Systems is still in business and happy to talk about their products old and new. This was one of the very first programmable electronic calculators. It is implemented with discrete plastic transistors and uses an acoustic delay line memory. Sorter Herman Hollerith invented punched card data processing for the Census of 1890.