From my nonexpert perspective and the apparent state of that thing, I would assume you would have an amateur rocket with an unspecified launch date. Even if it's safe, you'll save money with modern efficient models.
AusRenovation
This, and also externally this heater might look ok and "works" but inside might be full of rust-mud.
We have recently removed our old heater and the insides were pretty nasty, the walls have almost rusted away just waiting to pop.
Interesting looking basement.
I'm jealous. Walking height ceilings? Arches???
It puts the lotion on its skin....
In my non expert experience being a very cheap bastard there are a couple things that go wrong with water heaters: calcium buildup and the element....maybe the area has very soft water?
Calcium buildup can be removed with acid, delime solution or vinegar & the elements can be changed out rather than replacement of the whole tank.
Maybe the previous owner was a cheap bastard like myself and figured repair was worth it instead of replacement...either way, if it ain't broke don't fix it.
Those things are built, quite literally, like tanks.
It'll go at some point, so have some money put aside for a replacement, but you aren't going to save money by replacing it with a more efficient model.
If you're going to invest in a heat pump model, I believe they do better outside. So do yourself a favour and talk to a plumber about a good spot, pour a little slab for it, maybe even pre run piping.