Maybe I'm losing my mind, but I can't figure out why anyone would use that little screw on the back of the hammer to rotate the hammer nose. I have two 4-digit Contenders, one made in the first year, and both of them have a clearly visible screw slot in the hammer nose between the segments which are different heights, only one of which will strike a firing pin. It is a MUCH more substantial screw slot than that little thing on the back of the hammer, and the manual, which I still have, clearly states that is what is supposed to be used to rotate the hammer. Cock the hammer and look carefully. I have never seen a Contender with this type of hammer that didn't have a slot on the front of the hammer nose. In fact, the first model did not have that screw on the back; there was a tiny lock ring that held the hammer nose, the detent spring and the detent balls in. It was prone to popping off, and when mine did I ordered some detent balls, springs and lock rings (free, of course) and they sent me a new hammer assembly (also free) like the one we are talking about here. I managed to reassemble the original and still have it, but the newer version they sent is the one on the gun.
RonF