Interesting article. It does not directly mention the windows, but I don't see why an air conditioned car would need windows that open, except for a situation when the air conditioning fails and you want to allow some ambient temperature air to flow thru the car to provide some relief for the passengers.
The article mentions an order of 125 cars; 25 for non-electrified lines (presumably class P72) and 100 for electrified lines (presumably the EMU version, classes MP72c, MP72T and T72). However, the roster information I have leads me to believe LIRR ordered a total of 220 cars from Pullman Standard that were delivered between July 1955 and July 1956. I have the following information about these cars "as built":
2501-2522, 22 cars, class MP72c 2601-2674, 74 cars, class MP72T 2801-2844, 44 cars, class T72 2901-2980, 80 cars, class P72
Was there a follow-on order for an additional 95 cars, shortly after the first order of 125 cars? Is my information accurate??