I could take my ID to the library / police station, have it verified, and then get given a USB stick with 16GB’s worth of signed government tokens from a big bucket of unmarked hardware. I guess a bad site could still narrow down who I am to my nearest library / police station though.
Proof-of-age tokens that aren’t tied to my ID have the downside that they are transferable. Kind of like a case of beer is transferable from an adult to a child.
Is there a better way of keeping are-you-old-enough separate from who-are-you?