Door seals to toothpaste, usually I'm apt to run the train off the track!
Here's photo's of the door weather strip gasket from my '78 1300 Trillium
. Close to 3/4" wide and 1/4" high. The top corners are rounded and appears to be a basic closed cell black foam. Could probably buy at Lowes or equal.
This seal attached to the actual door and not the body of the trailer, I assume that is to what you were referring.
Might be compressed a little, but not a lot. Was stuck on with double sided tape.
I'm pretty sure it is original, very crumbly after 35 years!
And now back to your regularly scheduled program....4 out of 5 Dentist recommend....