buying used bottles.
welding bottles have to be tested and certified every so often. Those numbers are stamped on the bottle. My old portible 2 ft high ox acety set had not been used for about 15 years. when I needed to use them again and get a refill they were still good and the supplier traded for new ones. I had a friend that moved to the east and the moving co would not take the extra bottle he had in his garage. When I took it in they said it was too old, had lots of numbers stamped on it. They would not exchange for a full bottle. JUST BEWARE when buying used bottles, Make sure you can exchange them.