IHC used that cab for like twenty years, just small detail changes. For instance, those signal lights on the fenders came along in about 1959. Could easily be as registered.
Used to be good info here
http://oldihc.org/
but I see it's a whole different place than it used to be and I can't log in anymore.
Also the American Historical Truck Society has a great forum, good place to pop in if you love old trucks.