Mine is new castle I believe. Bought from a former club prez who purchased them from a distributor. Couplers were banged up so they were scrap or keggles. Cost was more than a $50 deposit.
Pretty sure I bought my co2 and propane tanks when I got them new. I am free to swap where ever I please. If I left a deposit on my propane tanks, I wouldn't have to sell them on my own when I move in the next year. I wish I could get my money back, now I have to settle for $15 on Craigslist or give them to a buddy that I know will appreciate them.
I don't think Airgas rents their tanks, at least not the locations I've used, if they did they would stamp something on them. Maybe they would buy my co2 tanks, but I'll just dump the gas and bring them with empty. sure as hell won't do that with propane.
Massive tanks for homes and co2 in the beverage industry maintained by a supplier, maybe your right.
Edit - forgot to mention that my old roommate bought a keg at a garage sale owned by our local brewery. He gave it to me to use as a keggle. I returned it and got a few 22's for him in return. I'm not a thief.