Those are AMG wheels that where standard on 2001 & 2002 SL600's. The rears are 18X10 and the fronts are 18X8. Midwest Wheel and Tire have them for $599 a wheel. You may be able to find them for less if you do some searching.
Buyer Beware: It has been documented through various sources that these wheels are known to develop cracks prematurely!
For an example, please see the following thread: 3-Piece AMG (OZ) Wheels
Our fellow R129 member 'robinp' found 8 in 10 rims of the 17" AMG (OZ) 3-piece' wheels having cracks between the mounting bolts to the centre bore.
The answers to most of your popular wheel size/offset questions (as well as most everything else you could want to know about these cars ) are located in the Blue Sticky section at the top of the page. Those are the AMG I 3-piece, and as others have said, finding a good set that aren't cracked without getting taken for a couple of thousand dollars can be difficult (ask me how I know!! And thanks Kim!!)
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