Hmmm!
I have oxy/acetylene, argon, CO2, and Tri Mix (for stainless mig) in my shop and I just take them into the gas dealer and they exchange them for me.
The only bottle I don't own is the TriMix and that belongs to the dealer and no other dealer will fill it. I also pay monthly rental on this TriMix.
However I own all the rest, no longer have to prove ownership. I just go to any gas dealer and they exchange bottle for bottle without regard to the inspection dates.
I think the idea is, they get the exchange bottles cycled through inspection and don't have to worry about refilling bottles that are out of date (the refill process determine if they are due).
Many years ago (early '80), if you owned your bottles, you had to show proof and if you didn't own any bottles, they had you make a deposit on "their bottle" and charge a monthly rent.
Now they don't seem to question owner bottle exchange. And if you don't have the the bottle, they rent theirs to you along with a deposit and the refill.
Something that you should be aware of, is the present day cost of Acetylene. I stopped using it about 8 years ago due to the cost and now use tig or mig for welding and plasma for burning. I still keep a small bottle around for silver soldering and make sure the valve is tightly closed. I estimate a simple gas welding or burning job can now use about a bucks worth of gas.. I have never liked propane for welding or burning. MAP gas seems to be common in industry but I don't have much experience with it.