Hello Christian,
It seems as if you have late-style 280 SL rims or something like that.
Can you read numbers on it? Original MB (at least steel) rims always have the part number imprinted in the center near the wholes where the bolts go.
Depending on the VIN, your car should have the
113 400 03 06 (like mine) or the
108 400 00 02.
The first one has three little pins in the center to hold the hubcap, the later has three nowses/edges for this purpose.
The change was made very close to your serial no. but I don't have the one right by my side now... :oops:
You can sometimes find these rims on ebay or so or someone else of us needs to get rid of his. I remember that Tom Collitt had correct 230 SL rims. Maybe he still has.
Otherwise mail me offline (achimahlert@yahoo.de), I will let you know possible sources where you can find some.
Good luck!
Achim
(Magdeburg, Germany)