You can get verification from CMPicon if you want. There is a $25 search fee whether they find it or not (they will). However, and in my opinion, I don't think it's necessasry. Your rifle is a rebuild which most are today. The only thing a CMP letter will show is that they sold it because there won't be any other provenance regarding originality or "correctness." It's not a "Collector" or "Correct Grade" rifle.

It really doesn't matter where it came from unless you are curious, the rifle stands on its own for what it is regardless.