I can find Rolf Brandt driving it throughout 1954, previously he seems to have driven a Porsche and one of Richard Trenkel's cars in 1953. The trail however goes cold from 1955 onwards .... until that is, I spotted it, unidentified, in the background of a photo of Tak's Maserati in the 1956 ADAC 1000kms at Nurburgring. (Revs Lib Stanford University again!)
Its number is hard to make out, but I think it is 36. If so, the drivers were Karl Busch and Karl Schwaneburg. I hope one of them is the driver in your photo.
Note to self .. must get out more.