This Z3 Coupe was posted on madwhips.com by WhipDaddy. He photographed the Coupe at Bimmerfest 2009. I’m not aware of any Sterling Gray Coupes owned by BMW forum members in the US. It seems to be a very rare color, but I don’t have any data to back that up, just speculation.
This Z3 Coupe has a set of wheels I haven’t seen before, but they look like OE BMW wheels. Edit: The wheels are Style 37. Along with the wheels, the Coupe has lowering suspension, but otherwise appears stock.