Thanks for all this great info.

I do have gauges, vacuum pump, new orings, and in fact cans of r12 and a can of r12/oil.

I’m not going to just throw r12 into the system and risk losing it and of course being a jerk with the atmosphere.

I don’t think the system has been fully open to air - in fact when I just touch the shrader valve a little pressure still release - perhaps that is meaningless.

I think I’ll evaluate the compressor and post some pics of it next.