I don't know the rule with CO2 tanks but it seems weird that neither of my acetylene tanks have a wheel on them you use a little wrench on the valve stub and it looks looks just like the pic of your tank without the wheel. The wrench is chained to tank though that may have something to do with it . I have a 10 lb one for plumbing and a 20 lb tank in the garage and they refill them all the time. I would think an open valve would be a little more of a problem with flammable gas .Both of these tanks are from the 50's
Maybe they were busting your balls ?
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