I recognize that furnace as I have one... it s a Hydro Flame ARS-10L or 10LX, 6,300 output BTU. I think the "L" stands for "Left-Vented" version. They were made to fit alongside the door of camper trailers or truck slide-in campers, etc. They are a very nice and durable gravity furnace but just a little too wide to fit in the side of the closet of a
Scamp 13. That would be plenty of heat for any size fiberglass camper. The gas valve can be replaced with a new Robertshaw 710 series fairly easily if needed. I'm keeping mine around in case I buy an Airstream or Spartan or something similar in the future. This would be a good find, someone should buy it so I'm not tempted!
John A