News from 2016, but I don't think it's been mentioned here before:
https://news.artnet.com/art-world/a...rency-784904Micro-engraver Graham Short, known for his almost impossibly-tiny works of art, has engraved five £5 notes with a minuscule portrait of Jane Austen.
After increasing their value to an estimated £50,000 ($62,000)—Short claims similar of his drawings have been insured for that amount—the 70-year-old artist and his gallery, Tony Huggins-Haig Gallery of Kelso, Scotland, surreptitiously spent four of them in England, Wales, Scotland, and Northern Ireland. A fifth bill was donated by the artist to the Jane Austen Society.