Upon further inspection, there are two problems with the crankcase vent restrictor theory. The "hole" in the center is just a dimple, so it is more of a plug. The other problem is that the crankcase doesn't appear to be vented; as in there is no vent line nor an opening in the case for one to attach, at least not on that side of the engine.
I did notice that this thing has a diameter that thing will fit very nicely into the I.D. of the cover guide pins. Maybe it was a manufacturing artifact that fell out the guide pin when I removed the cover? As I said, it fell into my drain pan; I didn't find it in the case. I've looked in through the Clymer manual and the IPBs and I can't find anything that looks like this little bugger.