On the earliest Contenders, the firing pin selector was in the face (front) of the hammer. It was a slot head screw type of thing that had the metal on one side of the slot machined lower than the other. The high side struck the firing pin. It was positioned so that the slot was right at the juncture of the two firing pins. Steel ball detents were used to hold it in the proper position, and you changed it by cocking the hammer and using a screwdriver to turn it 180 degrees. The very earliest ones were held in place by a tiny lock ring on the back of the hammer. It would occasionally slip off and the whole innards would go flying - very interesting. The balls were about the size of #8 shot, and I once used some such shot in an emergency while I waited for parts. Then they threaded the selector and used a screw from the back to hold it in. I never had one of those fail. Eventually, maybe because so many people started to use scopes, they changed to the slide selector. Probably because a lot of people didn't understand the internal safety, they incoporated a middle position "safety" in which a little pin protruded from the front of the hammer as a safety, and that's what you are describing before the advent of the "twist" type of selector, which also has a middle "safety" position. So, there have been (at least) four types of hammers and firing pin selectors.
RonF
