DiveSite:As the photo in THIS LINK shows, 3AL is stamped from the factory on tanks that were made out of the 6351-T6 alloy, not just the 6061 alloy. There is no 6498 alloy (that i'm aware of). I believe the 6498 that you speak of is an Exemption or Special Permit number. The Visual Plus 3 tester WILL in fact test the 6061 alloy. BUT with that being said, it is very UNLIKELY that a 6061 alloy tank will have a neck crack.
Thank you for correcting me! I do not know nearly as much about tanks as I do about stage theatrical lighting fixtures


VP3 will test it, but were there other models that will not? I could swear that somewhere I heard someone say that older testing methods on new tanks (and using the VP stuff on steel tanks) will usually result in faulty tests if not read by someone who knows how to overlook many "problems" that the data shows which don't actually exist.