Great stuff, though I prefer fully mechanical rather than motor driven machines myself — there is less to go wrong with them, and they are certain to outlive the electrical devices.
A small point relating to servicing these pinwheel calculating machines:
As with typewriter segments, oil introduced into the pinwheels is a distinctly bad idea. Pivots, sliders, and such were, of course, meant to be greased, but the pinwheels which are the real business end of the devices are meant to be kept dry. What this means is effectively that the machines should be lubricated sparingly. Short of complete disassembly, there is no way to do this comprehensively, so servicing such machines for most of us will be a compromise with what is actually possible to do within our lights.
This site has some excellent resources should the mechanically-inclined wish to delve deeper: https://www.jaapsch.net/mechcalc/index.htm . Be warned that the operations are said sometimes to take a couple of weeks rather than hours!
