Suncorite would not have been on the rifle in WWII anyway. Considering it was in service through 1961 (or4?) at least, the whole rifle probably got rebuilt to one degree or another several times, so having a late scope makes perfect sense, and there's no reason to assume that it's not correct given all the other clues. Very nice to see a well used rifle that is likely just as it was when it left service.
The yellow paint could be perhaps a visible indicator that the rifle was "going away"? It was liberally applied to the chests in many cases.