Assembly line silver grill question

[R68GTO]

I sourced an assembly line "bone colored" original grill for my COPO project. I noticed that one of the rectangular openings had a section of plastic "casting slag" left from when the grill was pulled from the mold (I assume). Also noticed that the NOS grill that was bought from a GM dealership and installed in 1979 had this same casting slag in the same spot so am assuming that replacement grills were made from the same molds.
My question is do any of you guys with assembly line grills have this same "defect" and do I leave that ragged slag or sand it smooth during the restoration?

[KevinW]

Yes, lots of casting lines/bumps on my factory grill too. So how ragged is it?

[William]

I worked in the plastic molding industry as an Industrial Engineer for many years. Guessing here, but I will bet there were at least 4 molds producing standard grilles for the production run. Since they were so large, there may have been another molding facility in CA for the Van Nuys plant.

Sometimes different color plastics run differently so there may have been a mold designed specifically for black molding compound. When molds are fresh from the tool shop they are tight and produce parts with minimal flash. Molten plastic injected under tons of pressure is abrasive and over time the molds wear down. As that happens, the parts have increasing amounts of flash. At some point the molds will be shut down and rebuilt to minimize flash.

Point being, don't look at a few grilles and conclude they all looked like that.

[R68GTO]

Thanks for the info guys, mold wear explanation makes logical sense as the same thing happens with metal stamping dies that I have some familiarity with.
With this info, I'm inclined to just leave them on there for the resto, it's an original grill, so that's how it was made in 1969.
Even better that my car is a late-build 09D car so a worn out mold makes sense lol.