Sanford Ink 1778830 Counterfeit Marker, 3/PK, Black, SAN1778830, SAN 1778830, Counterfeit Detector by Sharpie is specially formulated to detect bad bills. The technology reacts to the presence of a key ingredient present in papers that are not used by the U.S. Treasury. The ink marked on a suspect, counterfeit bill will change in color from golden brown to blue-black. An authentic bill will not produce an ink color change. This marker is effective on all U.S. currency. UPC Code 071641028784, Quantity 3/PK