Why were the Triarii differently equipped?

[Dan Howard]

No, it doesn’t prove anything, well to me nothing. It can also be interpreted that the soldiers are dismissed, and then they go to the state armoury, are issued their kit according to the wealth and age, then on the report date turn up.

The only reason to organise a muster into wealth groups is to determine who can afford to bring what equipment. It was a very common practice from the Bronze Age right through to the end of the Medieval period. Each group is ordered to turn up with specific gear and if a person can't afford to do this then he is relegated to a lower wealth group with less expensive equipment requirements. If he can't meet the minimum equipment requirements then he is refused permission to fight at all. The modern concept of a state owned arsenal filled with gear that is doled out to recruits is actually very rare historically.