If you have a multimeter, you can check for sure. Others correct me if I am wrong.
1) measure for OHMS across the + and - side of the coil. You should get something in the area of 1.5 ohms. This is if you have a stock 6 volt coil.
2) measure for OHMS from the ignition side of the firewall mounted ballast resistor to the - side of the coil. You should get 3.5 ohms. Also the readings you would expect from a stock 6 volt coil.
3) measure for OHMS across the + and - side of the coil. IF you get roughly 4 ohms, you have what they CALL a 12 volt resistor coil. In this case you probably do not have a ballast resistor on your firewall. What this amounts to is a 6 volt coil with a built in ballast resistor.
So where does the fact that you have a 12 volt battery/system come in? Its ohms law, but what happens is, by the time you have applied 3.5 to 4 ohms to the 12 volts, you get 6 volts to the points, which is what the points need in order to last a long time and work great.
In other words, for this vintage, there isnt a 12 volt coil. You dont want one. It would burn out the points on a non-linear scale more than twice as fast. The other concern with a real 12v coil and low ohm values is the HUGE increase in current you would have going through your wiring. You dont need a fire.
