The other dealer in town allowed me to purchase my tanks 30 years ago and has been exchanging tank for tank ever since. If you do not have a bill of sale you are usually out of luck. In Ohio the tanks that are sold to an individual have a smooth collar on top of the cylinder-leased will usually have something casted on the top of the cylinder.
Ditto on the dealer. Grab the yellow pages and find somebody that will work with ya.
Do you own the tanks ?
Some other independants will just swap tanks and not worry about it. They enjoy the gas business.
Laws in states vary some, mostly LWS rules are the biggest problem. I own
all my cylinders I have titles for all of them, we have titles in Illinois. I just
swap them at my local LWS. Most mine have smooth neck rings and the LWS
swaps them with smooth when in stock but as long as I have titles it really
does not matter. Airgas will not refill/swap my cylinders, so they do not get
any of my business. The other independents will; but cannot beat SJ Smith's
pricing so I stick with them, and the free delivery is alwasy nice. I do have
to pay a hydro charge every 10 years on the tanks to SJ Smith. They actually
track that. Actually around here generally 3 years of lease/rental rates are
about equal to purchasing a cylinder. The smart LWS's sell tanks, dumb one
lease them but once the owner moves he owns them... LOL
I would look for a better LWS.