" How can you tell if it is a 12 volt or 6 volt?"
Measure it w/ an ohm meter. 1.5 ohms or so on the primary (stud to pigtail) , it's 6v. 2.25 ohms or so, it's a 12v.
"I accidentally touched it and it burned the crap out of my finger. "
To get hot, the points must be closed. And to get that hot, you put full 12v battery voltage into the coil. The coil was not designed for that. See tip # 38
"Running inline resistor." Get a 12 v coil. Remove the in-line resistor. Make sure you have a working oem ballast resistor in the circuit; that's the only resistor you need. See tip # 30