Hi, I guess my youthful age prevented me from knowing about this. Looks like a Mech E's dream. <https://arstechnica.com/science/2021/12/the-remarkable-history-of-the-hand-cranked-curta-mechanical-calculator/> YouTube video describing its operation. <https://youtu.be/loI1Kwed8Pk> galen -- Galen Seitz galens at seitzassoc.com