"new printers and copiers that they bought have software that detects attempts to copy/print banknotes, and will tattle on them"
The way that copiers detect bank notes is based on something called the "EURion constellation", which is a pattern of circles patterend similarly to the Orion Constellation:
If you have a $20 bill handy, you will see they are expressed as the zeros in the repeating "20" on the back:
It's also on the Euro and almost every other major currency in the world: