All Nortons were 6v until somewhere in the mid 1960s, so all generator Nortons were 6 volt - as they left the factory. However, its the REGULATOR which really determines if its 6v or 12v. The original fitment black Lucas thingy would have been 6v, and set up as positive earth for the later 1950s. As the Parts Book and Owners Manuals would spell out. Cheers.