Should be a data plate somewhere on the camper. Usually right on the back somewhere near the door.
As far as a manual, the Internet has a lot of things, sometimes things that surprise you, but not everything. They didn't make many of these to begin with, and most of them have rotted away and are long gone.
Fortunately it's just a camper, so there shouldn't be anything that you can't figure out.
I know with my camper, the camper's "manual" was a few Xerox pages stapled together, very short and had very little information that was pretty much common sense, like, "Don't lick the blue water." Everything else was the factory manual for the individual components in the camper. Since those things are used on EVERY RV for years, you can find those manuals online and they will be much more helpful.
Putting 10-ply tires on half ton trucks since aught-four.
