Early flintlock TC rifles had a different lock from some of their last production locks. The shape of the cock and the hardness of the frizzen was changed. The newer frizzens are black instead of the previous case hardened coloring, and are suppose to work better. The flash hole liner was changed from a slotted liner, to one that used an allen wrench. I replaced mine, before even trying the older one, so I really can't tell if it's better, but the new one functions fine.