Last production date / availability of 82001B classic batt?

[Juergen Hofstaedter]

Hello calculator friends!

How time flys, I haven't been here for five years it seems (forum says: You last visited: 08-15-2015). Also didn't pay any attention to my two HP-65 calcs meanwhile. But recently I decided to make a battery holder for three AAA cells which is probably the best solution for rare occasional testing. This worked out fine and the HP-65s are are still functional (gummi wheel already replaced 15 years ago or so).
But to my surprise I found one of the original 82001B battery packs still in working condition! Wondering how old they might be, does anybody know when HP sold the last ones approximately?

Cheers
Juergen