My Gen4 and subcompact Glocks (basically, the models with dual-spring RSAs) look a little like that. It was explained in another thread that this was from the molds used during manufacturing, and that it has no effect on the pistol's reliability.
If it does cause problems for you at some point, I'm sure that Glock will make it right for you.
NRA Endowment Life Member
Ammo by Dillon and Hornady