Counterfeit Currency Detector Pen offers a quick, easy way to prevent fraud by easily detecting counterfeit currency. Specially formulated ink reacts with the starch in wood-based counterfeit paper to leave a dark-colored mark and expose false currency. This detection pen is easy to use and requires no training. Simply mark a small line on U.S. bills and observe the color results. If the bill is counterfeit and the paper is wood-based, the iodine in the pen solution will react with the starch and leave a dark brown or black mark. If the bill is authentic and the paper is fiber-based, the pen's mark will turn amber. Long-lasting antimicrobial protection helps prevent bacteria and fungus growth on the surface of the pen. Pen will not detect all counterfeit bills and should be used with other counterfeit detection methods.