Probably, I'm not sure about the details as I have never seen one mounted on the alternator.
It could be something totally different but voltage regulator is my guess.
Don't ask about wiring as I am only guessing here.
I have seen aftermarket alternators that had a voltage regulator mounted like that. IIRC, they were sold as a alternator/regulator replacement for cars with mechanical regulators. I also seem to remember them not being a Mopar alternator with a slightly different look.
I can't tell you anything more about them and a quick google search didn't show anything.
Six volt DC systems ended with Chrysler products at the end of the 1955 model year, across the board. Ford was the same way, as was Hudson and Nash. General Motors' last 6VDC cars and trucks were 1954 models.