Recheck the numbers on tanks 1 and 2. In July 1982 the DOT grandfathered various special permit aluminum tanks into the "3AL" standard and the special permit numbers SP6498, E6498, E7042, E836 , and E8422 were supposed to be stamped "3AL" at their next re-qualification (commonly referred to as the "hydro test"). Normally, I'd suggest that the "70980" is instead 7xx80 with the "xx" being the stamp for the independent testing company that did the initial qualification of the tank being mis read as "09", thus suggesting an initial qualification date of July 1980. However, the fact that your tanks are factory stamped 3AL indicates they were made after July 1982, creating an inconsistency in the dates.
Luxfer tanks made in the US after 1993 tend to be dual marked DOT/TC to allow fills in Canada as well (with tanks just "DOT" marked prior to 1993 grandfathered in in Canada). The tanks are DOT approved but not TC dual marked so tank 2, made in September 1998, was most likely made outside the US, and the M8201 on tanks 1 and 3 also suggests that while DOT approved, they were probably manufactured outside the US.
So, recheck all the numbers on tanks 1 and 3 and include any subsequent hydro test stamps. If DOT approved there should be an initial qualification stamp with an AABCC format with AA being the two digit month code, B being the stamped of the initial tank inspection firm and the CC being the two digit year code. On tank 2, the "09A98 denotes September 1998 with the initial qualification done by Authorized Testing as there stamp is a stylized "A" with an arrow in it.
Luxfer S80 tanks made prior to January 1988 were made from 6351-T6 alloy rather than 6061-T6 alloy and are prone to sustained load cracking. As such, they are subject to an additional eddy current inspection at each requalification and will be stamped "VE" to indicate they past the additional test. The scuba industry standard is to conduct an eddy current/visual plus inspection each year as part of the VIP, and since the eddy current protocols have been implemented over 11 years ago, there have been no catastrophic failures of 6351-T6 tanks due to sustained load cracks. However paranoia still runs high among dive shops and it can be hard to get any aluminum tank made before the (largely arbitrary) date of 1990 filled.
