I live near Philly and have never heard of the Philadelphia Terminal RR. I’m wondering if it refers to the car’s assignment, as in the car could be assigned to the Philadelphia Terminal of the PRR, RDG or B&O. It would be interesting to see a photo.
Incidentally, years ago, in my daily commute I used to take the subway to City Hall, walk to the Reading Terminal and catch the express train to Chestnut Hill. There was just enough time waiting for the train at the Reading Terminal to have two beers at the Gateway Tavern.