Aha, you are referring to the Edison when it was the overnight sleeper (and coach) train New York - Washington. I rode it a few times with that name and that schedule, but by then, on at least one trip, it also stopped at Philadelphia. But I also once remember going from Newark, DL to New York on a train that I recall being named the Edison, and it did stop at Princeton Jc., New Brunzwick, and Elizabeth and originated in Washington. My memory may be faulty on the name, however, but I was surprised that the train had the name of the former overnight sleeper train. The Edison that was the overnighter was replaced by NY Penn Station drop and pick-up sleepers on the Federal, which I also rode. I think at the time, the name was transferred to the train I rode from Newark, DL. You may be right that is was later than the 50s, possibly in the middle or late 60s. Beginning at age 11, in 1943, I rode what is now the NEC fairly frequently, even a youngster by myself, and it is hard for me to remember just which trip occured when.
Princeton Jc. was an important commuting point, and at least one Clocker into Penn in commuting hours in the morning and leaving similarly in the evening stopped there.
When you wrote Baltimore as first stop, you probably did not mean to exclude Newark, NJ. I am fairly certain the overnight NY-Wsh. Edison did pick up there.
Returning to the joint H&M - PRR Hudson Terminal - Newark service, there was dedicated equipment, all painted Tuscan Red, 50 cars owned by PRR and 50 by H&M and used indiscriminately. They all had PRR cab signal equpment in the cabs, which the regular H&M Stillwell-designed cars did not. The also had round end windows, unlike the regular H&M cars, but like the MP54s, and they were capable of higher top speed than the regular H&M cars, which they used between JerseyCity and Kearney.
If the PRR operation into Exchange Place, Jersey City, is considere