I have an M10 exhaust header that looks exactly like this, except uglier (surface rust and beige paint):
It was originally going to go on a '72 2002 which ended up getting traded for another car.
Since it's so rare and old, there is very little information about it. My buddy bought it from a guy in Paris (Ontario) a couple of years ago. The Supersprint one is stainless, and this is WAY too ugly for that. Does anyone know what it might be? Did Supersprint ever make mild steel headers in this same design?