Early bitcoin NFTs were not immutable.
In November 2015, XCPCARDS.com solved this for several cards, CHURCHHILL included.
This was achieved by including the following text in a bitcoin transaction:
The identifier v9w6yAKf 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.
Although the proof is from 2015, this particular card remained untokenized until 2021.
The file's full sha-256 hash in hex and base64 encodings:
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.