Money Detector Pen,Moeny tester pen,Exchange Pen, banknote detector,easy to use, 1) mark the note , for excample,with a cross,in an area which is lightly-colored and not printed on3) if the marking goes dark and stay dark, your bank note is forged!4) the marking disappears again after a few hours.5) it can be used for Euro and USA and other international banknote