So I pulled the heads off. What appears to be cardboard from cereal boxes has been used as gasket material. The first stage head is slightly rusted with a bit of pitting around the the centre of the head and towards the finger valves. Second stage looks really good considering it sat outside in semi-equatorial conditions for who knows how long. I bought this thing based on the fact that it turned over freely and hissed and puffed at the same time.
I pulled the cylinder offs and those bores look to be in working condition. No scoring or visual signs of excessive wear. I actually had to disassemble the entire top end just to be able to get this off the back of my truck into the garage. I took all the loose pieces and soaked in a simple green and water solution for a few days.
Yesterday I cut new gaskets by hand from a sheet of gasket material and I tested some thinners on the paint (if only I knew someone with a compressor to run a sandblaster haha

) It seems to be some sort of 1 pack paint and has started shriveling off the barrels. I will scrape the worst of it off and then get in with abrasives to prep for paint.
As to model, the data plate reads Type 30 5&3 x 3 1/2. I believe this is then a model 235. I see there is a port for some plumbing from the top of the 2nd stage cylinder. There is also a port on the side cover of the bottom end. Should these two be connected to each other?