Looked through a half dozen didn't see any dates. We do not make any warranty about effectiveness use or abilities.
Dude, I sell pants. We are not safety supply.
We do not recommend
Jumping out of planes with the army surplus parachutes
Running through fire with the Nomex Flight suits
Shooting the Army Helmets or vests
Climbing with Surplus rope or Fall arrest gear
Geezuz, guy's complain the Rain suits aren't water proof.
We sell these masks as "novelties" what ever abilities you project onto the gear is on you.
I can tell you what the Army used them, for but what you do with it up to you.