Sanford Ink 1778881 Counterfeit Marker, Black, SAN1778881, SAN 1778881, 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 071641028791, Quantity 1 EA