These are some very nice game progress stamps.

http://thefoxisblack.com/2017/04/19/prove-youve-traveled-through-video-game-worlds-with-pixel-passport/

They would be great as NFC/Amiibo tags:

https://www.theverge.com/2017/4/12/15223338/zelda-breath-of-the-wild-nintendo-amiibo-hacking-ethics