Might as well dive right in. A few years ago I purchased this very nice Hamilton 987, 17 jewel wristwatch in a 14K white gold filled case from a watchmaker friend. Of course it didn’t work. I finally got around to working on it recently.
All it needed was a replacement for the broken mainspring and a cleaning. If you look carefully you can see where the spring is broken.
This was one of those great watches that just sprang back to life as soon as I dropped the balance cock into place.