Rick, let me look around, I know I have a couple of newer style and I think I might have an original "somewhere" LOLHi all, I'm trying to find the metal door frame which is approximately 17 3/4 X 11 3/4 and is just to the left of the entry door and frames the refrigerator vent.
Rick
I did find what I have, they are all bigger that the dimensions you were looking for, the metal original looking one is a Dometic, 20 5/8" x 11.Rick, let me look around, I know I have a couple of newer style and I think I might have an original "somewhere" LOL