And there should be the possibility too win cash prizes! You know what, forget the age thing.
This, but seriously. Maybe some age token company might also run a raffle or other promotion.
EDIT: Because age verification tokens will likely be a commodity, low-margin business with little differentiation. So I assume companies will do stuff to make their token more attractive than the competition.
In my state, they scan your ID and check it with the state's database. Store policy is usually to do it for everyone, even if they obviously are above the age of 21, and the state mandates ID checks for anyone suspected to be 27 or below.
Also after I had a certain number of birthdays, clerks have stopped demanding my ID. So my purchases are pretty much anonymous.
The card should be issued by a private company, or ideally, multiple companies. And it should be a scratch-off card with a unique code, so that codes can't be tied to transactions.