Dodge B250 Ignition Condenser
RRR is correct, that is a noise suppressor. It's really not needed with plug wires today, they have built in noise suppression.
Not quite true. The plug wires radiate like antennas, and the coil circuit induces noise directly into the 12V wiring. Secondary interference is different, then, than primary interference. That condenser is used to help that. But it also does something else. It actually provides a low impedance path to ground for the coil primary pulse, and in some cases MAY help spark performance.
In these old girls, the biggest sources of interference were
Secondary spark (plug wires)
Primary interference (coil primary circuit)
Alternator whine (there is a cap in the alternator)
Instrument limiter, or IVR (it has a cap as it constantly switches on / off and can "pop" in the radio
And, the radio itself had a filter on/ in the radio to try and suppress the last of the noise. Even the wiper and heater blower motors can cause noise, and so can the signal flasher.