Early bitcoin NFTs were not immutable.
In November 2015, XCPCARDS.com solved this for several cards, GOXCARD included.
This was achieved by including the following text in a bitcoin transaction:
xcpcards.com/GOXCARD Ou2qM3XD
The identifier Ou2qM3XD is the jpeg's checksum which proves the card's design. Since this text is engraved on the blockchain, the proof can never be tampered with, nor can the timestamp be disputed.
This makes GOXCARD one of the first real crypto cards!
The file's full sha-256 hash in hex and base64 encodings:3aedaa3375c3c2d87d4613e24f5263c80dfb4ebace8de2a88721f4997d4bd0d6
Ou2qM3XDwth9RhPiT1JjyA37TrrOjeKohyH0mX1L0NY=
The identifier is a 48 bit truncated hash.
This is sufficiently strong, yet short enough to have the text fit inside a Bitcoin op_return message.
The below cards were notarized by XCPCARDs.com
Most are from the Spells of Genesis project.
Click a card to view its details.