I should say on the sticker on the compressor unit. I recall seeing something like 125 lbs on the low side.
I doubt you can find some R-12, but you can use R-408. Do not use R134a, it causes the R-12 lubricate to gel.
My cold machine compressor stopped working, so I cut the 110v compressor out of a mini fridge and brazed it in place of the 12v compressor on the cold machine. It was R134a so it's easy to charge.
I run it off an inverter when I'm not on shore power.
If a man must be obsessed by something, I suppose a boat is as good as anything, perhaps better than most. A small sailing craft is not only beautiful, it is seductive and full of strange promise and the hint of trouble.
- E.B. White