Are they actually steel bottles or as is most likely aluminium bottles , if they have a number like AA6061 stamped among the bottle markings then they're aluminium and have a 10 year test period so won't need testing until 06/2020. If they are actually steel (check them with a magnet ) then they have a 5 year test period and will need testing 06/2015. This assuming the 06/10 is the born date stamped into the bottle markings.