Dri-Mark Products, Inc., of Port Washington, New York, has introduced a new counterfeit detector system, which adds an ultraviolet light to help identify counterfeit currency. The Counterfeit Money Detector Pen produces a dark mark on fake bills and a light-colored mark on authentic currency. The UV light in the pen cap provides a second authentication test by revealing the embedded micro-printed strip in genuine currency. The UV light will test several thousand bills and it comes with three button-cell batteries. A simple detection guide and instructions are also included. The light also detects the hidden security thread on checks and credit cards.