Powerful yet compact ultraviolet penlight reveals UV-sensitive security markings on 1996 series or newer U.S. currency denominations greater than $1. Counterfeit detector pen detects bad bills by marking a line on the bill; if the mark turns dark, the bill is suspect. UV light also works on many foreign currencies, major credit cards, passports, travelerï¿½s checks and more. Batteries (included) last up to 20 hours; LED diode up to 50,000 hours. Counterfeit Bill Detector Type: UV Light Pen; Marking Color: N/A; Counterfeit Indication Mark: Dark; Currency: U.S.