I have 29 Mosin Nagant rifles and only one has the aftermarket sn stamped on the receiver. The rule of thumb I have been told and gone by is NEW receivers don't have a mark under the tang. My NEW doesn't and my 43 Tikka 91/30 doesn't. All of the others have the maker and year stamped on the tang. My bound book has the barrel sn listed and it passed muster with the ATF. Don't sweat the sn. Unless, you live in a state where the rifle has to be registered. As posted above, buy one and try it out. Mosin Nagants are like Lays potato chips......chris3