Another possibility would be an Allegro. My mother's was chromed, then a translucent blue finish, fading to all chrome towards the ends. Swiss bike. I don't recollect the BB threading. Very beautiful bikes, campy components and weinman brakes.
allegro from this time have a proprietary shell with deep sand cast marks and a prominent lip on the fixed side. the serial number is in an ingot brazed to the side of the seat tube. seat stay treatment was different. fork crown used was different. shells were swiss threaded. mondia/juvela shells are french threaded. there are a few other differences as well...