I would think that the line up pin is the pin in the hammer to keep it from rotating, My KP2sc has a round hammer w/two lobes and no pin (see a PGP hammer for one with a pin). I would think that allowing the hammer to rotate is better as it allows the lip(s) to wear evenly all the way around so they dont wear out like nelson style bolts.
The second sounds like a hammer for the later KP3s that had a pull tab safety as opposed to a rocker on early KP3s and all KP2s.
Originally Posted by Tescrash
Almost only counts in horseshoes in handgrenades....