A motor that uses points ignition instead of HEI.
The side terminal supplies voltage to the coil during starting, as you said, so that when the starter tries to use all the power, the coil/points will get as much as possible. When you take your foot off the start button and starter stops drawing, that side terminal goes dead and the coil/points get their voltage thru the resistor. The resistor reduces the voltage to about 9V. The standard 12V conversion is done with a 12V externally resisted coil, a ballast resistor and a side terminal switch. A person can do whatever they wish otherwise.
