How is the US currency protect from forgery?
While a lot of the design goes into creating subtle hard-to-copy differences, some counterfeit features are quite literally embedded into the paper. A security strip and a colored thread are just a few, among many.
How do you spot a transport of US dollar bills?
If you ever meet a truck driver with a gun, telling you he's carrying halloween candy, chances are you have just run into the truck transporting US currency paper from the mill, to the engraving department.