Austrian Post launched "Crypto Stamps", which are available as physical stamps in Austrian Post's online shop, or as digital stamps through their OnChain-Shop.
The physical version (edition of 150.000) is connected to its digital NFT equivalent, and each stamp comes with a wallet address which contains the NFT. As for the digital stamps, which can be bought via the OnChain Shop: According to the data available via the shop and the wallet address, digital stamps are limited to about 500. Once only 100 are left, they increase in price. By the time of writing this note, there are only 56 pieces available, and the price of the next stamp is set to 187.38 EUR. As both, physical and digital stamps are (connected to) NFTs, they are unique, can be collected, traded, and their provenance can be tracked.