I've had some luck buying used cylinders. I did remember what we were taught about tank markings. When I bought a pair of AL80's virtually unused, sat in a garage for 3 years, I was able to point out and explain the meaning of the markings, the fact they'd need a VIP immediately and hydro in a year. I offered them half what they were asking and aquired 2 Catalina AL-80's. They were never used enough to be abused, and this will be their first re-test, so I don't have much doubt they'll pass. On the other hand, I aquired an older Luxfer AL-80 and made a rather low offer conditional on passing hydro, with me paying for the hydro. The gamble did pay off.
On knowing the markings and checking when you rent. I was picking up 2 of mine from my LDS, when a diver arrived in with tanks from a shop in Toronto. Both "in" hydro, but near the end, neither with a VIP sticker. She was a little p***ed off at the store she rented from, when my LDS refused to fill. Had done 2 dives the day before and planned on doing 2 more on the way home. Her buddy had gone on ahead to the dive site, which was not on the direct route home, so she was goin gto have to drive there and then return home, paying for the days rental (she didn't think she'd make it in time to return them that day). We suggested she point out the lack of a proper inspection sticker and ask for at least a partial refund as she had to end her trip when she couldn't get fills. Not sure if she tried another shop (I've had fills in all 3 local shops, all are very careful about checking hydro/VIP, so she wouldn't get air in this town.
! Now, in high school, when I liked tinkering with my Dad's '71 Ford Torino, I could tell you how much gap those spark plugs needed. Diving is not like bicycle riding - you do forget some things.
