I was in Central Terminal for the first time in about 1964 or maybe 65 (I was 4 or 5 years old). At that time there was a partition that separated the very eastern end of the main concourse (connected to and still in use for arriving and departing passengers going to the platforms directly over the tracks) from the western end where the restaurant was located. The partition was bolted to the floor and I would guess 8 feet tall. The waiting room (south side of the main concourse) was also blocked off at that time.
There was still a small "grill" (seats for maybe 50 people) operating in the eastern end of the concourse, but it was not the "Restaurant".
The NYC offered the Terminal up for sale as early as 1956 (IIRC). I would guess the restaurant closed in the late 50's or early 60's. It was definitely long gone before PC or Amtrak.
In 1964/65 the newsstand at the SE corner of the main concourse (on the "public access allowed" side of the partition) was still operating, my parents bought me some taffy in a NYC themed miniature vinyl travel bag (about 6" long). I still have the bag, but the taffy is long gone.
Would like to learn when the Restaurant shut down and more history about that partition.