On older American cars, there was a large resistor, called a Ballast resistor that even the flow of current to the ignition coil...this was typically found on the firewall (near the ignition coil).
There were a series of capacitors for noise suppression, usually about three. Since the older radios were most often AM radios (and tube-type before 1963), they would pick up anything the remotely resembled background noise. The Delco caps were a body-grounding design, found at the generator/alternator, the voltage regulator, the ignition coil, the back of the AM radio and occasionally mounted the the back of the instrument cluster, usually at the Amp gauge. I don't recall the Delco stock number, but they were much smaller than the mystery coil pictured. These Delco caps were about 3/4" in diameter, had a tab attached to thier steel body that would allow them to be screwed down, and had a 3 or 4 inch pigtail of 18 gauge wire with an offset brass #10 forked terminal on the end.