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?