Well there you have it - thx again Gwhite !
Here's one for everyone to examine (the only one - so far - I've found with race history) :
911 660 9057 / now Willi Rabl 935 below :
1992 Bergrennen Ecce Homo Sternberk ( Willi Rabl / 17th overall / 1st grp. H)
You can read more about it on J. Starkey's website :
JOHN STARKEY CARS :: CARS FOR SALE
I don't know exactly when is was converted to 935, or what is was doing prior. But the earliest I find it is 1989 (strangely with Rabl, which does not necessarily coincide exactly with Starkey's history - he has it going to Rabl in 1990)