I looked. The class 72-IC-1 features the end doors you describe. 59 of them were delivered. They look just like Harriman cars except for the windows and end doors. I am not an expert on the plastic GGD Harriman cars, but I believe their brass series had several different body types.
I do have most of the PSC variants.
Roof arch is just like the other Harriman cars. Best photos for comparison I could find are on p.25 of the Morning Sun "color guide" book. The term "sub" is new to me - I took the time to ride in these things during overnights in Burlingame.