The wife's uncle recently showed me a rifle he's had for years which he bought at an estate sale. It is a Pennsylvania style full stock in about .40 caliber. The condition is poor but the workmanship is still very obvious. It has been converted from flint to percussion by the addition of a percussion hammer and a drum /nipple assembly screwed into the vent. The drum is crudely made from a threaded bolt of about 5/16ths diameter.
It is quite interesting to note the different skill levels between the maker and the converter.
Steve