Many Airstream models where available in two floorplans, Twin (a twin bed on each side of the aisle) and Double (usually a folding "Gaucho" on one side of the aisle, with cabinetry on the other.
Starting in the '70s, some of the longest trailers were available in a "rear bedroom" floorplan that could be had with twins or a fixed double that didn't fold up (a very few had a rear gaucho, I've seen them in documentation but never in photos or in person.)
Some of the small vintage trailers had a "corner double" like a few of the modern plans, where there's a small bathroom in one corner and the bed is in the other corner. The gauchos that run along the length of the trailer and the corner doubles mean that one sleeper will be up against a wall and have to climb over the other to get out of bed.
It seems that the majority of people selling used trailers don't specifically say which plan it is, and if there's not a picture that shows the bed area you'll have to ask. It seems to me that most of the nice ones for sale are Doubles, because I prefer the Twin plans. It's all about perspective, y'know.