That isn't the original rear bumper, so the holes you mention must be from the Chrysler factory when the bumper was stamped. It was made of expanded steel with aluminum edging around the outer edge. It got scrapped just a couple of weeks ago. Didn't know there was any interest in it. I have a used engine radiator that is also destined for the salvage yard, along with a lot of other car parts that I no longer have the cars they go to. Can't keep everything forever, and expect someone else to clean up the mess after you are gone.