D&RGW's "Snack Bar Car" vs D&SNG's "Concession"

After seeing Wil Hata's scan of this fan trip in 1982, it brought up some random thought in my head.

The Special at Rockwood by Wil Hata, on Flickr

I noticed the 212 in the consist here, and gravitated towards the fact that it was not lettered "Concession" which piqued my interest. The roofline was what made me realize it was the 212, but the lettering on it threw me for a loop. Mr Hata says that in the photo, it was labeled as "Tefft". From there, I broke out a copy of 'Cinders and Smoke' which confirmed its use as a coach in this time frame, not becoming a concession until later.

But before its coach configuration, Osterwald labeled it as a "Snack Bar Car", which to someone my age, would probably call a concession car anyways. Was there a real difference between the two when it came to layout? Was part of it a coach and the other section dedicated to food service? Having been used to GCRy's ex-PRR Clocker lounges being used as a concession car (with tables in one!), the concessions on the NG have always felt cramped (unless its 566 or 64 with the doors open) and can only imagine them in their current configuration (being younger than the genesis of their current configuration also compounds things for me).