So, I was draining the oil and when I pulled out the drain bolt, I found these little heartwarmers attached. I've taken off the valve covers and checked the springs, retainers (and seats as well as I could) and didn't find the source. However, the size of the bigger piece almost perfectly matched the outer edge of a retainer and I'm leaning toward it being valve spring seat.

http://imageshack.us/a/img35/5397/img0120ipw.jpg
HUGE IMAGE

 

I would say you are correct.

 

I'm fairly certain #5 is the culprit as I don't see the seat poking out from under the spring anymore. I'm going to send it to the machine shop and let them replace all the retainers, locks, seats and seals on both heads.

 

Looks like a seat to me also. It's easy to replace those bits yourself. No need to pull the heads even unless you suspect valve damage.

 

Yeah, it is a piece of seat and apparently a chip off a timing tooth.

Odd thing is, I haven't had seal seats (that's what it's from) since I went dual springs 25,000 miles ago. I have shims under there now and it's definitely not a shim fragment. I'm guessing it must have been stuck somewhere in the engine until I poured a can of Seafoam in the oil.