I would be surprised if there many USA coupes with original paint, since a lot of those cars had metallic finishes. At one point (1974), I had a 1972 2002 (Malaga), a 1972 2002 tii (Polaris Silver) and a 1972 3.0CS (Fjord Blue). Both the tii's and the CS's paint crazed, as was typical for BMW metallic paints of that era. I still have the CS, but the body work was completely redone to eliminate rust and then repainted.
When you consider that the CS rusted pretty easily and that the metallic paints almost always crazed, it is unlikely that many E9 coupes remain with original paint.