I believe that pinfires, being an obsolete cartridge, are exempt certification but the position regarding a replica is less clear.

Consider: A genuiine antique muzzle loader kept as an antique or curiosity and not fired needs no certification, but a replica is an S1 firearm unless it has been properly de-activated.

The situation is further complicated by the apparent fact that item in question would probably disintegrate if actually fired but this might not necessarily be a factor. A (now deceased) shooting colleague of mine had properlly certified S1 firearms. He also had a really badly corroded 12 bore shotgun wall hanger. I have seen the item and trust me there is no way it would survive being fired. Never-the-less a zealous FEO noticed it on his wall and the upshot was removal of all his guns and revokation of his FAC. It was some years (3 or 5) before he was able to regain his FAC.

This is a problematic area and might need a court case to set a precedent!