Here’s a photo writeup of a lab for our Optical/IR instrumentation class. We had to disassemble an old clock and put it back together, ensuring it worked. It was great fun, although challenging at times. There’s quite a lot of gears, and we had to contend with some exploding parts 
All told, it took us about 3.5 hours to take the clock apart, figure out how it worked, and put it back together again.
