I really appreciate the quick and informative responses. I turned the bike over, and tried to read a serial #, and there is one stamped into the metal where the pedals are installed (is that the lower bracket? Please excuse my ignorance). I really couldn't make out much - there are 6 characters: the first two look like 55, I can't make out the second 2, and the last 2 look like 24. I'll try to drag it outside and see if it's any clearer. I'll also try to take a few pics - it really is in nice condition.

Unless these bikes suddenly surged in value at some point, it's probably not a real rare or valuable one - I certainly didn't pay all that much for it when I bought it, secondhand, from a bike shop in Miami. But I've changed nothing on the bike - all the components are original, and in good condition. Someone asked about size - I think it's a 26", but I'd have to measure to be sure.

If I can find any more significant markings on it, I'll post them. Thanks again to everyone.