I'm sure there are those much hipper to the 1242 knowledge than I. However, I always thought it had something to do with the first ever Oakley television spot produced.
Hammers, for example. Hammers are indeed from the 1st M Frame (Mumbo). But they became "hammers" when I took the original straight earstems from the 1st production tool and didn't like the look or fit when we assembled the 1st pair. So I stopped production. I then bent the straight earstem out and back to create a "detour" around the temples so they fit better and it widened the overall appearance of the frame so the lenses "hung" better underneath. We had to lengthen the tips since I used up some distance with the bend. I kind of "hammered" them into a new shape. We had to delay shipping for two months until the new "hammer" tool was done. The original "straight stem" tool came in handy sometime later when baseball players needed the M Frames to fit under their batting helmet. We pulled out the original straight stem mold and finally put it to use.
Hammerfangs
Found on 2nd gen M Frames. Extended earstems comfortably accommodate any head size without touching your temples.
I'd have to check but I recall Hammerfangs as being a Zero feature. I don't think we used this terminology on the Gen 2 M Frame. (I could be wrong here).
Remember, when you get info from someone inside Oakley, they probably had to ask someone since they weren't likely there at the time. And there is a lot of mutating explanations of history going on. Someone "thinks" he knows, says it and the next guy takes it as fact.
I'm here to help. I am happy to fill in any information gaps. The only thing I ask is no PM's (please). I just don't have the time to respond to them properly and it makes me feel guilty if I can't answer all of you personally!