How to pass age verification on the US Playstation store? (I’m old enough, but how will I have to prove it?)

I have a US-based “Playstation Network Account” on which I plan to buy a game via pre-paid PSN code “cards”.

I’m reluctant to add the money to the account, because I’m not sure how Sony will do the age verification for the game.—As a foreigner I might not have the documentation they expect!

I do remember seeing a German age verification in Germany (on the PS4), which accepted a German ID card (the numbers on it), but I don’t remember if that verification triggered because that PS4 was in Germany or because that PSN account was German...

US accounts do not seem to have age verification (at least not in this case). Voucher added value can buy rated content without further checking.—You can also test this with “free to play” content. It should trigger age verification for $0, but it doesn’t. I tried that with some titles, which clearly carried the same rating symbol as the game I was interested in (“M–Mature 17+”).

And it turns out that the ESRB-rating used in the US (and Canada, Mexico) is not legally binding for sale in the US according to Wikipedia (rating comparison and ESRB).

Games in the highest rating “AO—Adult Only 18+” (the only ESRB-rating legally restricted in Canada and Mexico) are not even “published by Playstation”.