Thanks Kevin for posting that pic...Did you find any signs of it being mask off on the back side to keep from getting on the argent? I would guess the amount of overspray would vary as well?
I don't recall looking for that kinda evidence
but the back was not painted with silver, only from the front, so the back edges did not have silver. It appeared to be painted on a rack facing front and the body color being painted to cover the outside edges that show. That is where the overspray came from. There was little overspray on the bottom of the grill.
You are correct they were molded in grey plastic and painted silver, probably before they were shipped to the assembly plants... here is an original RS grille in DETAIL... These pictures were taken of the same grille the same day with the same camera.
If you have a piece of original silver grille and cut into it... there is no metallic in the grey, even if cut sanded and polished there is no evidence of any metallic in the molded plastic.
That leaves 2 possibilities either they were painted argent before they were shipped to assm, or maybe there was a deviation on what Mark was saying in that some type of an argent release film was sprayed in the mold when they were cast (this is my imagination thinking about how else a coating could be applied during a molding process, I have no idea if it is even possible in a production environment.)