The extra name ring was probably added by the importer (so the serial number relfects their business, not Zeiss Jena's). There were a lot complications regarding trademarks after WWII. Zeiss Jena was forbidden from using prewar trademarks (like Biotar, Tessar, etc.) when selling products in the west. Additionally, in the U.S. only the official importer was allowed to sell lenses with the Zeiss name on them. So grey-market imports or small import/export businesses would have to rebrand the lenses - some times all they did was paint over the Zeiss name and the lens name (or grind them off!), and that was that. Better importers would put on a new name ring to cover the original.
This was also true of cameras, sometimes when you remove the importer's name plate, you'll find the Contax name engraved underneath - or ground off underneath.