You also asked whether it needed an external resistor, and if it still has the original coil then yes it needs an external resistor. if it has a true 12 volt coil then no, it does not require an external resistor.If you are chatting about my post.
As I understand it, Bob's Jubilee was 6 volt, positive ground when he got it. A local tractor guy converted the ignition and charging system to 12 volt, negative ground replacing the generator with a GM alternator. The 6 volt starter motor was left in. Not sure about the lighting, I don't think they work anyway.
I'm guessing this is a popular conversion?
There are coils that are labelled "12 volts, external resistor required" and lots of folks argue that these are true 12 volt coils, but they are not. They are designed to be run in a 6 volt system with no external resistor or in a 12 volt system with an external resistor, and the label is a warning that you need the resistor in a 12 volt system.