I was trying so hard not to spill the beans on this one. That is one of the nicest green Radiobikes I have seen, and certainly the nicest example in private hands. This is also the only single-speed model I have seen.
So far, based on research, the green models were offered in 1955-early '56. They were only occasionally advertised. Red was heavily advertised, and was offered from 1955-1958, the final model year. I have only seen two advertisements for the blue model, which appears to have been 1955-only. The low advertising for blue explains its rarity for sure. As far as I know, Scott M. and myself own the only blue Radiobikes known. Scott's is mint. I have heard rumors of others, or parts, but no photos or serial numbers to back up the claims. I hope more are out there, even if just a handful it would be nice to see other survivors.
I would LOVE to have the serial number off this green model to add to the registry thread. If I get enough serial numbers, I will start an Excel spreadsheet.