They came out in late 97, so no, HPA wasn't what I would call common, but the solenoid they used would self destruct if used with CO2 due to the RoF and ice crystal formation. And the insides of that solenoid are pretty wimpy looking.
And NOS batteries are fine, it's only after they have been charged and discharged that you start having problems really, mostly due to battery 'memory'. At least they aren't like LCD's, battery dies in one of those and it's time for a new board
