I've seen a few on ebay that were made in the 70's and evn some made in the 60's. Would these still be usable?
Keith in West Virginia
entirely possible that a tank from the 60s or 70s is still usable. I believe one of my tanks that is still good is from the mid to late 70s.
A scuba tank must be visually inspected annually, and must be hydrostatically tested every 5 years.
I would suggest that you have the seller send you images of the hydrostat sticker(s) to verify the last time the tank(s) were hydrostated.
As a scuba diver, I personally would not buy a tank, no matter how old/new it was, that was not hydrostated in the last six months, 1 year at most. Scuba tanks can be very dangerous, and anyone selling one should, IMNHO, extend the common courtesy of making sure the item they are selling is safe for the buyer.
Hope this helps.
The hydrostat is an interesting test. They take the tank's inner volume, and force 120% of that volume of water into the tank (water doesn't compress like a gas, so the tank has to expand). Then they measure the deflection (aka swelling) of the tank and make sure it's within limits for the given tank. All of this after a thorough visual inspection of the inside of the tank and especially the threads.
Once it's broke, it stays broke until somebody fixes it.