I see what you're talking about with the indentations from a type 2 or 3 bb. I was wondering about that. The problem is, my friend bought this as a bringback from the family of a guy that was a colonel. He trusted the people, and for him, that means something. He was told that there IS paperwork on this, and I'll get it when they find it. Also, since I know the stock is an IBM, and probably a replacement, but all the metal is perfect (including the barrel) and original Underwood, it would make sense for the stock to have those marks from it's previous life on an IBM. On the sights, I'm also not so sure. These are not marked at all. The replacement sights like these that I've seen have all been marked I.R.C.O. This one is blank. There are a lot of parts on this gun that are not marked at all. I have been told that Underwood didn't mark all their parts. Also, on the later carbines, they did start using adjustable sights. This is not an early carbine that would have had flip sights, this adjustable sight is really appropriate to the serial number and age. What I think I have is an original carbine that stayed with it's original owner it's whole life. That owner was a lifer, which does explain the replacement stock and the pristine condition that it's in. He would have kept it in good condition, not used it much, and kept all the up to date parts on it. This guy had a small but VERY impressive collection. He did not keep anything that was less than amazing. I know this gun truly is one of the rare ones. I AM looking forward to getting a hold of some books though. I want to know everything I can about it. I guess I'll try to find information on sights next. =D