Crypto Stamp is an innovative project launched by the Austrian Post in 2019, merging traditional philately with blockchain technology. Each physical Crypto Stamp contains a hidden NFC chip and a QR code that links to a corresponding digital version, or "twin," which is a unique NFT secured on a public blockchain like Ethereum or Polygon. This initiative aims to bridge the gap between the physical and digital collecting worlds, providing collectors with verifiable ownership and a new way to interact with their stamps. The project has expanded to include collaborations with other postal services, such as PostNL of the Netherlands, and continues to release new editions.