a portrait of reptilla would fetch many XMR
A bowling date with the Dude would fetch many XMR at auction
A precious-metal XMR signature "ring" would fetch some XMR
Signet ring? How to cast digital signatures into iron is bejond me. Thinking about ways, technology wise. This would not work on a techlevel below smart RFID tags. Is it possible to not only power (wireless, like Tesla tried) the tag's chip but also a led requesting yes/no on payment, additional button?
Stephenson's Cryptonomicon on my mind, but memory fails me. Been some other story featuring a geek's heritage engraved into a ring, symetric AES cypher to decrypt stuff of importance. That wretched tablet where I stored this ebook was a mistake to obtain.