I think the production number is between 100-150 according to a so. cal Schwinn dealer that has one, or had one on display since new.
I have heard, more than once, they were offered to the top tier dealers as a promotion back in the 50's. Several were used as rentals on the east coast boardwalks.
I have a red one and they are a hand-full to ride, the old drum brakes are more for sound than braking with three up.