I bought a 1919 250-3000 from Randy a few years ago. I think it's the butt stock that's off a couple hundred or so. He lettered both numbers. The action number came back with all the usual info. The butt stock number came back stating no rifle with that serial number ever left the factory. The consensus back then was that the butt stock was original to the rifle,seeing no rifle with the butt number ever left. I have both letters in my safe. Maybe Randy remembers the details a little better.
Letter stated no rifle with those butt stock serial numbers appeared in the ledger. So that rifle almost certainly left the factory with that butt stock on it. The letter doesn't prove that, but it sure does make a really strong case for it. What it does prove is that nobody cannibalized the stock off another gun.
The 48 EG is most likely right, especially if the fit and finish look right. It would not be a deal breaker for me if it looked right to me. In my opinion it doesn't diminish the value of the gun, especially if it has condition.