So, for fun the 1972 model is a Phillips Power Converter model PC 151-M-2
115 volts, 2.7 amps, and 60 (watts I assume but the sticker is torn).
12.7 volts DC Current, 15 (amps I assume but sticker is torn).
The wiring diagram on the inside of the cover says one wire goes to/from battery, the other wire to the "motor". I assume "motor" refers to any DC item and that's how I used it.
Through the vents I can see one giant transformer and one blue bean-sized something, maybe a diode.
There is a "Batt/Conv"switch to select battery only or converter. I am not sure if when switched to Conv if it just powers the "motor" or also sends volts to the battery at the same time. When the Conv is selected the lights were always brighter than the battery was ever able to make them.
I think how I wired it was I ran the battery positive into the converter and then the converter had one output for 12+ and that powered the "motor" and everything DC in camper.
If I remember correctly, when AC power is to this it still hums, so maybe is charging, or on, but I will have to wire it up and test it to know. Its been 4-5 years…The converter was on its own circuit breaker so I used that as the on/off switch.