A "12V" coil primary winding is actually made to operate correctly at around 9.0-9.5 volts, which is what is available from a "12 volt" battery during a cold start due to the load the starter motor puts on the battery. Once the engine starts and the charging system tops off the battery, system voltage is around 14.5 volts. The ignition ballast resistor drops the voltage the coil sees during normal running to prevent the points from burning. "Resistor" spark plug wires were invented in the 1950s to reduce radio and television interference caused by the magnetic fields developed around copper or steel core ignition wires. The ballast resistor works in the low voltage primary ignition circuit. Resistance plug wires are in the high voltage part of the ignition system.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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