This is very interesting.
If you enjoyed the video about anti-counterfeiting measures on bank notes, you might like this video here about the EURion Constellation, a somewhat secretive series of rings seen on many bank notes worldwide that tell a computer that what it's looking at is currency. It is just one of the many ways a copy machine or computer application prevents copying or altering of a bank note.
YouTuber standupmaths posted this video below about why he thinks Australian banknotes are some of the best in the world. And it has nothing to do with its design (some love them, some hate them) but more about how they increase in value and in size based roughly on a mathematical log scale.
He includes a comparison with British Pounds as well and notes that the UK Pound not only increases in length as the value goes up, but it also increases in width as well. Some people don't like this because it means the notes don't fit nicely in a stack, but if you consider the pure usability and accessibility of bills with these features (especially for people with disabilities), it's quite a good thing.