That's my cheap Dutch nature. Instead of having the holes in the bumpers welded shut, then rechrome them, I decided that, with simple antenna caps (that's how the auto shop I bought them at called them) I would achieve almost the same effect. The are chromed plastic (no discernible difference with chromed metal), have a small black plastic washer at the bottom and attach via a plastic nut that you tighten by hand from inside the bumper. They come in various sizes and are very cheap. I did the same with the front bumpers. I'm sure they can be found at any auto parts store, and probably even at places like Eckerd Drugs, K-Mart etc carry them.
Cees
white 1969 280 SL