This guy came across my bench with a mangled hairspring. I also found the impulse jewel to be broken off and missing. So I replaced the spring and fit a new jewel. Fitting the jewel was fun as I needed to shellac the jewel on the impulse plate. Always fun to use my staking set as well. Watching these old guys come back to life is very rewarding. The stories they could tell.
ouch! 
roller table and jewel 
roller jewel fitted 
donor hairspring 
hairspring and jewel replaced
The Dialed In Watchmaker 