If you want to learn how things work, I suggest buying a broken half-frame camera cheaply and learning how to fix it. Specialized tools like spanner and clamp wrenches may be called for, but these can often be home-made. Too bad plastic half-frame cameras like the Soviet Agat 18 aren't common in the US of A, but there seem to be plenty of Olympus Pen-series cameras around, and they can sometimes be had cheaply because they're suffering from decades of neglect.