I was cleaning my G43X and noticed the following (pic). I have been using Glocks since 1997 (G21). Used them in competition, LEO, and concealed carry. I looked at my gen 3 Glock 19 and gen 3 Glock 26 and both have the same "mark" in the same place as the 43X. Guess I'm not as observant as I thunk I was
What causes this?