I do commercial refrigeration for a living and I am that guy who can fix the ancient industrial stuff with no paperwork, markings etc. Those are old reclaim tanks for pulling refrigerant out of equipment. Usually yellow and grey in color. What kind of refrigerant is anyones guess without a pressure reading. And pressure reading would tell you nothing if they mixed refrigerant. On the other hand if it is uncontaminated r22 it is going for about 1500 dollars for a 24 pound jug right now. If you know a good hvac guy that is your solution