My bottles (54 total) 150 cu/ft Nitrogen for stouts as well most of the rest in 250 Helium, 215 Oxygen, 260 Argon and 260 C-25 for Mig are all stamped 3AA dated 30's and 40's by the Linde Gas Bottle Company. These all came from Germany during the Hitler era with the Swastika restamped into a full square to be "PC". (screwed up their history markings JMO). These history bottles being all 3AA stamped still pass hydro allowing +10% overcharges. Thicker steel than newer bottles plus their history hence refills only no exchanges. One 300 cu/ft bottle has 1927 date a 3AA still takes +10% fills. On Co2 in 20#'s and 50# steel only. I can deal with free bottles with extra weight vs aluminum, they sit outside the keezer. My 1951 72 dive bottle still passes hydros starting on the 4th row of stampings a hand me down from dad, priceless to me. I agree by the above reply on aluminum with diving, sucked with the boyancy I traded a free 8 month from new 100 bottle for older steel twin 50's that became singles. Just don't let a steel C02 go empty and sit hot and cold sucking in moisture creating carbonic acid eating away the steel inside, this is a slow normal process why speed it up? Old and steel here.
Bier Jagdwaffe... Bier 30 zeit.....~~=o&o>..........