This one really baffles me. It seems to be a cross between all the wedge-shaped Opel concepts of that period - the 1969 Opel CD and the 1975 Geneve and GT 2 - and, indeed, the Cavalier Sportshatch. But none of them have those strange vertical stripes in the rear side window. I can not find any mention of any other Opel concept of that same period - and still I have a very strange feeling I have seen the front end of that car before. Frustrating!