This is an Airstream Argosy Class A 20’ motorhome (1974-78, this is a 74-76). Already a rare and lumpy specimen, this one is an oddity in that it has the roof typically left to shuttle buses and commercial use Argosy models. Most of these commercial use vehicles weren’t equipped with the full interior including bathroom, kitchen, etc. so I am wondering if it was converted some time later since someone is obviously living out of it.
Seen in SE Portland