I think you will find the only two years were 1969, 1970 for that layout in the Caravel
and Globetrotter unless you go back "many" years or look at newer models.
One trailer that you may not know about is the 1970 Safari "Special" which was the same layout but in a 23' version. It basically had a Caravel/Globetrotter back end, with an "Overlander" front end. It's a great layout, lots of room. I own one and it's great!
Here's a link to some info that might help.
Document Archive - Airstream