A PhD student at the University of Cambridge’s industrial laboratory was granted the opportunity to experiment with a new Xerox color photocopier in 2002.
He naturally chose to photocopy money as a student. But when he did, he discovered something strange. Instead of a new stack of paper notes that would mislead exactly zero merchants, he discovered a message written in various languages reminding him that copying money is unlawful.
This isn’t the case with all copiers, with some refusing to print and others printing but doing a poor job so you don’t ask for it again.
Kuhn, a security researcher, was not about to let the mystery go. He looked over his notes and noticed an interesting small pattern on them.
“On the 10-euro banknote, I spotted this particularly obvious pattern of little circles,” Kuhn explained to the BBC in 2015. “I stared at it for a while and I saw that the constellation inside this pattern was recurring.”
He next performed tests, copying the pattern on a sheet of paper and attempting to replicate it. While it printed the pattern in black and white, when he switched to colored circles, the printer informed him that it was unlawful to print money.
Kuhn termed the pattern the “EURion Constellation” due to its resemblance to the Orion constellation. Copiers, printers, and software such as Photoshop identify the pattern and refuse to allow you to do anything wrong.
Governments, understandably, are tight-lipped about how these things are coded onto banknotes, though Kuhn speculates that the spacing between the circles is detected on Euro bills. The same constellation appears on notes all around the world, prohibiting countries such as the United States from creating money.