Rugers are not cosmetically perfect, I have MANY GP100's and among the cosmetic flaws are a casting void on the frame behind the hammer on one 6" GP100, it looks like a chunk of the frame is missing...........also have one with a rough looking firing pin retaining pin like that.......have another with a front sight channel so tight that any front sight I put in has had to be "fitted" with a file and would then be super loose in any other GP100. One of my favorite GP's has a rough chunk filed out of the channel where the pawl rides, looks like a Ruger tech removed a casting burr on his way out the door at 4:59 pm and just jammed a rat tail file in there,, yanked it a few times and threw it in the box.

This gun also had an overlong pawl and the cylinder wouldn't close after the gun heated up from a few cylinders, I had to touch the pawl with a file to fix the issue....... The gun works fine now, I'm not worried about it.
I have paid much more for a few brand new S&W's and got a gun that looked like it was polished by a 3rd grader........I paid $700 for a 617-6 and do not expect my new guns to look used out of the box.......I sold it soon after because I was tired of looking at it.
I could probably go on with other flaws, but I still love my Rugers and trust my life to them every day.

They work, they're affordable and they last forever. If they came from the factory perfect, they would cost double what they do now.
Also have other "flaws" in many of my Six series guns, such as a barrel that was over polished on the sides so now it's oval shaped,
They aren't always perfect, but they work. I wouldn't worry about it, it's not a Korth, it's a Ruger
