NSU based , ran at the Nurburgring 1000kms or 500kms, don't know name
I've found the car, thanks to Georgano and his large book of motor racing. I thought it might be one of the Spiess cars , but it's an NSU-Gepard being driven by H.P.Richrath on the Course de Cote de Dudelange in Luxembourg. The caption believes it is 1968 or 1969, although I would have said a few years earlier by the style of the helmet and overalls.
(Georgano names these 2 makers of racing NSUs and a quick Google Image search comes up with this one photo.)