Years ago I bought a little 20cf argon bottle at a swap meet for use
with my MIG welder and though I got some odd looks when I brought it
to a gas supply place to get filled I've been using it ever since with
no problems, having gotten it filled at a number of welding and gas
supply places. Now I'd like to get a bigger bottle and I've seen some
at swap meets/garage sales but I want to make sure what I'm getting is
on the up and up. Most of the bottles I see have some sort of company
name marked on them in one place or another (either stamped into the
tank or on the gas label), does this necessarily mean the tank was
stolen/not returned to a gas supply house? Will I have trouble getting
these tanks filled? I assume gas supply houses keep pretty good track
of their bottles so I find it hard to believe that all of these are
stolen. Any suggestions or advise?

Matt