A tooth! That's a fun one.
We got a machine at the store that a grandmother had died, and left her sewing machine to a daughter. She brought it in, without looking inside. When we opened it up there was about $1000 in cold hard cash! And the daughter didn't know. We closed it up quick and called the daughter, and didn't work on it until she came to claim the money. She was so surprised!
Another one was a vintage Singer with the cork screw vertical shaft. I took the top off and there was mouse poop in there. Cleaned that out, and the cork screw shaft was binding up. When I looked down in there, there was corn and berries that the mouse had stashed.
Here's a sewing machine "Hall of Shame" if anyone wants a good laugh.
http://shesasewingmachinemechanic.bl...-of-shame.html