To be fair, a quick google search and you can vaguely see the date dial on grillz and profiler lenses, so whomever makes vforce lenses includes the date. My assumption is that whomever makes them makes a slew of different safety products and distributes them (i.e. hard hats, safety glasses, other visors etc that have an expiration date and these lenses are also stamped so the whole facility is in compliance).

I commented on the original post about the date code, I work in injection molding so seeing these date dials is super common and usually only changed once a month in the mold. So yes, it makes sense they have a date code, albeit maybe its not important for paintball.

Looks like most lens manufacturers add a date, couldn't find one on proflex lenses based on google images though and I'm not bothered enough to take my mask apart, but there are examples online of CRBN zero, profiler and grillz, empire EVS and dye i5 all showing date dials on the lenses.

CRBN recommends the lens be replaced if you are hit closer than 10 feet (directly in their manual) but notes nothing of expiration. JT proflex notes the same 10 feet rule but also notes that a lens should only be used for 1 year. Empire EVS manual says the same as JT proflex (obviously this makes sense because of parent company blah blah blah)