Found two old pentax SLRs from the 1950s-60s abandoned in the garage by previous owners. Decided to open them up and get them going again. It's a marvel looking inside them. These cameras are operated by entirely mechanical systems: with a little bit of love and care, even their timing systems still work.
Debugging mechanical issues by looking through manuals and watching gears and levers whirl is a nice break from spelunking through code.