Most people are aware that United States currency has been printed with magnetic ink, but most really do not know how magnetic it is. This is easy to test and might surprise many skeptics. Simply hold the bill as in photo 2 below and you will see that it is very magnetic. This is more dramatic when using a neodymium (rare earth) magnet, but a regular ceramic magnet will work nearly as well. The magnetic ink has been designed for use in machines that process bills for change and in ATM's. To deter counterfeiters, the bills also have fluorescence, security strips, and the background behind the presidents image has different spacing, as in photo 3. (Left to right, $1, $5, and $10).
Counterfeiting money has been around since the beginning of the first striking of coins for commerce. Roman coins have been found that were struck by counterfeiters. The penalty for them was probably death!
The author has an eclectic background in chemistry, electronics, writing, mental health, and community action...Ken