if they are stolen by an employee and marked sold you are ok! just kidding. most everyone who is selling the tanks will know if they are owner tanks or rentals. sometimes they have the word SOLD stamped into them sometimes it is a triangle and series of stars. if you feel you can't trust the person you are getting it from just ask to run them by your local welding supply and they can tell you. most people will be upfront with you. if you get a chance to get one of the large O2 bottles buy it. you can't buy them anymore they will only let you lease them. so if you are going to own them you have to buy them from a individual. and they are the cheapest to refill. someone else may know more about telling. i just bought a large full argon bottle today for $65, i am excited.
