The experts have yet to reply, and I say that respectfully. But I'll give it a stab.
The stock looks to be original, although altered. The barrel band keeper appears authentic, but the barrel band probably needs to be flipped around so that the "U" is on the right side. The slings swivels wouldn't be original, either. Pull the butt pad off and see if there are any holes for storing a cleaning rod. This could give you further indication of it being an original stock.
The barrel could be a replacement explaining the 3xxx and the front sight that doesn't appear original. And there also appears to be file marks on the left side of the reciever that could explain why there are no markings that would give us the best clue of the model and perhaps more if the serial number was still there. Maybe you could do a little metallurgical forensics and see if any of the original stampings can somehow be seen.
It seems as though somebody years ago wanted to disguise this rifles military lineage.