I find that hard to believe, search "2003 Mercedes SLK320 Relay Control MOdule", the 2003 SLK230 version also works.

THe RCM has a very high failure rate, in the three Roadsers I've owned since 2009, two have failed. THey fail so much, we have a guy in Arizona who, for $65usd, replaces all relays and reflows the board. He has fixed several hundred since 2008.

I agree with Zip, buying used is not what I'd do. That one's board looks good - but they don't show a good photo of the relay contacts, which are paramount to the car running.