On your Tractor with the broken tooth, any way to look into it without taking it completely apart and use a camera or bore scope and see what things look like?? Not familiar with that tractor but there has to be a place to get a scope into it and just fish around to see if you can tell where those came from, if nothing else, you need a good bore scope anyhow, might be worth a lot if its not bad enough to do a tear down.
Just a guess but a clutch pack if you have clutch linings in the filter, the tooth probably came out of the housing in the clutch pack along with the linings, probably the clutch packs you use when loading the pans is where I'd look first if you can see inside at all. A pack would be a really cheap fix if you can narrow it down. I'm not sure about where those clutches are at?? do you need to do a complete tear down to do them or check them?? Just guessing probably way off, but you asked for thoughts and idea's.