Thanks a lot for the replies. I had all kinds of speculative ideas. A bracket from which an outdoor table would hang; a center support for the awning. As usual, the most simple solution is the correct one.
We live in the county, literally the width of one street north of the city limits -- thank goodness. The only limitation we have is that we can't have anybody living out of a trailer. Fortunately nobody has tested the distinction between an extended visit and "living". Even more fortunate, I've got a carriage house/shop, so the project is happening indoors. The shell has been off, the frame rehabed, the deck replaced and the shell replaced. Now I'm near the end of the first-pass polish and will soon begin resealing seams and replacing loose rivits.
According to the serial number, it was a twin. But, it was gutted when I got it. We're relocating the bathroom to center curbside next to the refrigerator. I'm going to put in a queen with the headboard at the rear. It's going to be tight but at least on paper it fits. I moved the curbside window a little further back to accomodate the plan.
There are terrific bargains to be had in the local real-estate market if you have an ample down payment. As they say on the Price is Right, "Come On Down"!