I have the Erie Lackawanna set with the same type of car without windows in the middle. A diner perhaps?
A lounge car would have part of a side without windows. Are there windows on the opposite side?
A kitchen car would have a door on the side to accept supplies.
Yes Chas, you are correct. The car sans windows in the middle is the dining car.
Could you show a pic of the entire car please?
I believe it is the "dining room" half of the two car "kitchen/dormitory + dining room" set up that the PRR (and I'm sure others) used on some of their passenger trains - floor plan of D85c (not my website and not affiliated with owner of site). It's hard to see on the floor plan, but the wall behind the bar section didn't have windows. It always bothered me that Weaver called this a dining car, but didn't include the second half (kitchen/dormitory car) in the sets - they should have also included the D85d in the sets. Also, I believe the Weaver car had the "blank" section on both sides of the car and it should have only been one side.