Glock 43X - What is this?

[LOBO]

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?

[AZ6K]

Just looked at my 43X and it looks similar - they look like machining marks to me

[LOBO]

Just looked at my 43X and it looks similar - they look like machining marks to me

That's what I was thinking too. Just something in the manufacturing process. I just never noticed it before, and it looked "weird" for lack of a better word.

- Chris