I have been looking through more of my "635 files" and came up with this car. Unfortunately no chassis number, and you gents may well know of it.
Was for sale in January this year by a German outfit called GS Motorsport. They sent me the following:
"BMW 635 CSI Original 1982 Car built by BMW, Works Car, Ex Brun.
1984 and 1985 win this car the 24h Nürburgring
1984 Felder / Bröhling / Peter Oberndorfer BMW 635 CSi
1985 Felder / Hammelmann / Walterscheid-Müller BMW 635 CSi "
I'll keep looking for other cars...
Cheers!