Sorry for thread bump, but I’m working on some of this myself.
Near as I can tell, Mazda Sports Corner never had a logo, since it was started by Takayoshi Ohashi out of Mazda Auto Tokyo (Mazda’s largest dealer at the time.)
Historically, I think this is the closest to an origin design:
Later, it looked like this for a short time before becoming “Mazdaspeed.” But again, no real logo.