Clay,
Sadly, John Beardis 100% correct in every respect.
Original 03A3's were made up from a distinct mix of a distinctly known parked finish, and blued parts. The 03A3 you purchased is an assembly of parts that have all been through an arsenal rebuild and all parts refinished with a later park. You are correct that the stock probably came along later and the hand guard doesn't match it. They were most likely put together with the other parts at some time.
Regardless, it's not a collectable grade 03A3, but will make a great shooter if it's in good condition.
Was it sold to you as a collectable grade? Did you know the seller?