I can't tell from the pics. Is it wrapped? If so, it could have been painted and that can damage the tank. If Aluminum unwrapped, then I've not seen any rated over 3xxx psi. It is also unlikely, (unless, of course, someone messed with it) that the rupture disc didn't blow first. Aluminum has, under some circumstances, been known to stress fracture, that is if it's cycle stressed to a high degree. That is why you don't see 4500 psi AL tanks, the lower rating keeps the cycle stresss to less than 30% (IIRC), so I seriousely doubt there's a 5500 psi AL tank on the market. Keeping the cycle stress below 30% calculates out to an astronomical number of service years before a stress failure. Read up on it, it's easily found information.
There's more to the story......