Welcome to the Forums!
Shari has posted several good clues, and to her list, I would add that if the coach is a 1964
or earlier, it will have a "door-within-a-door"; while 1965
and later, the door will be one-piece. Another identifier is the jalousie window -- 1964
and earlier have a set beside the entry door; while 1965
and later do not have the jalousie window next to the door.
Good luck with your investigation!