The lock is from a 12ga shotgun. It was obviously used quite a bit. On the frizzen face, the first strike area can be felt, and the flashpan fence does have a slight dent. Internally, the lock is in excellent condition. Serious mainspring.
Incidentally, when acquiring a ml gun, it is a good idea to drop the rod down the barrel; this one stopped short about 2 3/4". Got out some #5 or 6 shot, dried up disintegrating cloth, and I don't know what else. Doesn't appear to be black powder. The bore isn't half bad. It has a plain hooked breechplug, with powder chamber is drilled into it, like a patent breech. Flash hole has a silver coloured vent. Clear now from vent into the powder chamber and bore.