I looked at a grade 2 Damascus 12 ga Smith yesterday. It is early as it has the firing pin bushings with set screws. It also has a, for lack of a better way of describing it, sort of a ball bearing on the round lump which fits into a recess in the frame. There is also what looks like a disc with the serial number in the round lump. The questions are..what is this variation called? and is it rare/unusual? I dont know how to describe it. Thanks Lawrence Kotchek