It's a 12" set, pretty much the standard size for B&W by that time.
The cabinet is Plastic, Bakelite was long gone by 83, at least in TV's.
It has discolored from age and the fire retardants used in making it, it was probably plain white originally, many colored sets such as white, purple and pink, suffer from discoloration as they get older.
There are ways to restore the color, see here:
http://videokarma.org/showthread.php?t=259066