Of course someone on Reddit already has an answer: https://www.reddit.com/r/AskHistorians/comments/38u3av/how_did_this_multiplication_wheel_from_a_1917/crye1o0

Of course someone on Reddit already has an answer: https://www.reddit.com/r/AskHistorians/comments/38u3av/how_did_this_multiplication_wheel_from_a_1917/crye1o0 https://www.reddit.com/r/AskHistorians/comments/38u3av/how_d...