The main thing I'd want to know is if the tank is in good condition. If it has a weak spot or two, it could explode when pressurized. That never ends well, especially if a person catches shrapnel. I've seen pictures of this that make me rather leery.
I don't know how to check the tank, other than disassembly of the compressor as needed for a visual. Nor do I know if a visual is sufficient to determine safety.
Before I was aware of this, an old compressor of mine developed a leak in the tank. turns out it was rusted through. I got quite lucky it leaked before it grenaded. Due to the compressor's age, I took it part to recycle what I could. Discovered the electrical wires going into the motor had missing and cracked insulation, so the leak saved me from possible electrocution. It was time...