Thanks guys for the input, I didn't know I was missing the good rear sight. It has something "simple" on the dummy receiver right now. The dummy receiver I believe is a Phily Ord. STEEL receiver. That sucker is HEAVY! No way it is alumin. I think there is an ATF letter somewhere along w/ the kit that I saw that was addressed to Philly Ordnance, that's why I think it is their receiver.
The only part that is not so "new" looking, that I can tell, is the barrel. It has some light surface rust and pitting near the wood handguard? areas, and although the barrel looks mirror and the grooves looks good, there is a "ring" about 1" behind the compensator? It's really hard to tell unless you look very closely down the muzzle of the rifle.
One of the old collectors told me it's okay and should still be okay to shoot but it's more of a shooter grade barrel than a collector piece. The ring is created by 2 rounds hitting eachother and expanding? He said that's common. Is that right?