My first guess was FED too, but then this wouldn't be a surprise, Cosina is too new in the market, Contax didn't stay long enough and was too expensive even compared to Leica in its days.
Hm, I doubt it was Nikon or Canon, don't know anything about Crown and Argus.
It must be FED or Leica, Leicas are everywhere and FEDs often come in disguise like Revue and such.
No, it must be FED.