Bob - On my 1966 230SL, my screws (4 total) are flat head, slotted, countersunk and not plated since you don't really see them. However, I was at my dealer last month to order 2 new chrome covers (called box pillar covers) and the new replacement part did not fit my car. So I had my 2 potmetal covers rechromed and used the original screws. The dealer said the screws are not available. You may want to contact the classic center in California to verify this. The listed part numbers for countersunk screws in my parts book are 0000 63 008129, 007987 006146, 007516 004200. Footnotes say these screws are different for various chassis numbers.
Jack Schmidt
