My aunt and uncle tried to do EVERYTHING legal when the registry came out. They sat down with all their guns in the living room and tried to register every single one of them... This included the 1868 .577 snider enfield that I have on my wall, which was given to me a few years back by her as a family heir loom.
Point being, when she tried to register it she couldn't, as there was no serial number, no readable proofs and the cfc lady finally just gave up and told her that it 'probably' doesn't need to be registered. Even though the 1868 stamp is perfectly readable and the rifle really does look over 100 years old, even the guys at the cfc had no idea what was legal and what wasn't back in the day.