I ***ume that "jump seats" got their name from the WWII paratrooper planes with the benches down each side for the guys to use before they jumped. Anyway, that's my story and I'm stickin' to it and why I'm calling the rear folding bench in my '52 Chevy panel truck "jump seats". Has anyone seen this kind of thing before? They look like an add-on and possibly not factory, and may be newer than the year of the truck. The hardware looks to be in great shape but the upholstery is petrified/roached so I don't know. The project isn't actually started yet but I know I'm keeping the seats. (Not the fronts. No-no-no-no.) (Don't worry about the hacked window. That's coming out of there and getting fixed.)
My village used to be a big health spa. Had jitneys to bring people between hotels and rail road. Your panel would work good for people or luggage. Was only a half mile ride. The rest of the year a local could make money doing milk can runs between the farms and depot.
A row across is probably more common. Starting and stopping sideways couldn't have been too comfortable. I'm thinking the fold up was to make room for various gear or goods with occasional folding down for a tradesman to pick or sort parts. I didn't show a photo of the p***enger side wall which has a row of open top compartments out to the width of the wheel tub hump. I'm leaning toward fabricating a full or partial hinged lid that matches the bench pad. I think the real story here is that this stuff survived without being gutted somewhere along the way.