Outside of what looks like file use on the hammer it is hard to get a perspective of the relationship between the hammer and the trigger without having another good set to compare this to. Look for example at your photo as it is showing the present engagement. Now imagine what would happen if one of the engaged lips breaks off. (particularly the one on the trigger) . Then someone recuts the notch to create a new engagement just like it was, but now the location has moved and the relationship of the hammer and trigger change, and the hammer is in a different location of travel when the two are engaged . That's what I think has happened in this case, and most like the trigger notch. I really can't be certain so don't take my word as gospel . In my early post I mentioned the hammer - I should have said hammer, or trigger, or both.