I have two 10 lb nitrous bottles (from NOS) that appear to be in perfect condition but way out of date. One I bought new in the mid-90's, filled a few times, and haven't used since then. Anyway I'll need to get them DOT-recertified before filling. I believe the stamp is good for five years. There does not seem to be any place in southern Missouri to get it done, though. Local welding gas place doesn't. One speed shop in Springfield (still 2 hrs away) sells N2O but doesn't recertify. They might have to go to St. Louis (3.5-4 hour drive from here!)... Any thoughts? (Crossposted on Moparts).