That "period correct" alternator is almost six inches in diameter and well over a foot long, and has a close resemblance to a generator other than the size. It required a pretty sophisticated regulator, and was used mostly on medium-duty and big trucks. The 55 amp generator can be recognized by the ball bearing rear end plate it has, and it required a special 2-contact regulator that had a pretty complicated adjustment sequence. It was used on cars like the Olds 98, the Buick Roadmaster, and most of the Cadillacs with lots of electrical accessories, and commercial vehicles like delivery trucks that did a lot of starting and stopping in the course of a day's work. Most of those heavy duty generators had a 2-sheave pulley to handle the load of the heavy charging current they could produce.
Jerry
