Dri-Mark® Smart Money Counterfeit Bill Detector Pen, U.S. Currency, 12/Pack (DRI351R1) 1 DozenDri Mark Smart Money Pen Highly effective and inexpensive tool for detecting bad bills. Simply make a small mark on U. S. currency. Chemically sensitive ink works instantly. An amber mark passes the test, while a dark brown or black mark fails, meaning the bill is likely counterfeit. Works on all new design U. S. currency (bills series 1959 and later). Global Product Type: Chem Pen Counterfeit Bill Detectors Counterfeit Bill Detector Type: Pen Marking