The Schneider Counterfeit Detector Pen is a simple yet highly effective way of detecting counterfeit UK or foreign currency notes. The Schneider Money Checker Pen works on most currencies. It will display a grey or brown mark if the note is a forgery and a clear or light mark if the note is genuine.Perfect for any bank, retailer or anyone who handles cash regularly, the Counterfeit Detector Pen is a handy and portable way of ensuring peace of mind, and an essential tool in the fight against the rise in increasingly sophisticated forgery.. The ink disappears on genuine notes after a short time.. Suitable for use on new ?5 and ?10 polymer notes