Peter, the NYRB 2500-2599 are the same cars as the NYRX 2500-2599 cars. If you look closely at this photos of the NYRX cars, you can see the the B was repainted or stickered as a X.
Both the ERDX 11000-11049 and NYRB 2500-2599 were converted from NYC lot 743-B boxcars. Under MDT-NRL specification 244. These were converted by DSI under construction lot 936 (different from NYC Lot 936).
The ERDX cars were for Eastern States Farmers while the NYRB cars were for NYC general service.
All were insulated cars, no ice bunkers, no mechanical refrigeration.
There is a small almost inspection sliding door on the B end between ribs just to the right of the centerline between the brake step and brake wheel. I don’t know if this qualifies for ventilation or not, as it’s not on the A end of the car.
There are drawings of these cars in the files of the NYCSHS. I don’t have them saved to my ERDX-NYRB file. I will have to go look for them.
Michigan City IN
NYCSHS Modelers Committee