How does a counterfeit detector pen work?
If you have looked at the most recent $20 bills from the U.S. Bureau of Engraving and Printing, you know that they have an army of security features designed to make counterfeiting more difficult. The most obvious of these features is the “20” in the lower right corner written in color-change ink. There’s also a security strip embedded in the paper to the left of Andrew Jackson that is visible if you hold the bill up to the light. Other new features include micro-writing, a watermark and very closely spaced lines (for example, behind Jackson’s face) that are harder for a counterfeiter to reproduce. All of these features are nice, but no store clerk is going to stand and hold each $20 bill he or she receives up to the light to check for a security strip! It takes too long and it is not a flattering pose to strike… The counterfeit detector pen solves the biggest counterfeiting thr
