Never seen a comressor tank blow but, I have seen a pressure vessel
(Boiler)that blew during hydrostatic test.
When I was working in a shipyard, someone decided to cheat and put air on
top of the water to speed up the test.
Blew a six foot hole in the side of a ten foot tank.
There is a lot of energy in compressed air/gas.
A tank that old should be hydroed or at least boroscoped.
A hydro is really easy if you can get your hands on a hand pump.
The safety cage might take a little fab work.
Fill it solid with water and then pump it up to 150% of working pressure.
I emphasize the safety cage just in case it does blow.
Anyone know of gas/welding companies that might offer the service?
Your mileage may vary, don't try this at home and all those other legal
disclaimers they throw in at the end.