Looks original to the trailer. I have a '67 Safari that has it's original water heater, or so it seems. I had the original Hydro-Flame gravity heater in my
Caravel, and took it apart and rebuilt it outside the trailer. Your water heater may be workable, but from a value standpoint, I think it's the exterior cover that has value, and a newer modern water heater might be what you want to do. I'd un-install it and go through the device. The Hydro-Flame gravity heaters have asbestos inside, so I'd be prepared for something similar if you tackle a refurb/rebuild. My interest in preserving my Hydro-Flame against Ralph Nader's better recommendations were to be able to heat without any electrical power, AC or DC. Knowing if you have an intact combustion chamber which won't leave CO inside the trailer might be difficult to ascertain. Your controller also has Mercury inside, though if all tubes are intact shouldn't pose an environmental hazard to you. Jerry