Dri Mark CFDUV87B Counterfeit Money Detection System, Ultraviolet Counterfeit Money Detection System. Powerful yet compact ultraviolet penlight reveals UV-sensitive security markings on 1996 series or newer U.S. currency of greater than $1 denomination. 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, travelers checks and more. Batteries (included) last up to 20 hours; LED diode up to 50,000 hours. Counterfeit Money Detection System. Powerful yet compact ultraviolet penlight reveals UV-sensitive security markings on 1996 series 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, travelers checks and more. Batteries (included) last up to 20 hours; LED diode up to 50,000 hours. UV light also works on many foreign currencies, major credit cards, passports, travelers checks and more. Powerful yet compact ultraviolet penlight reveals UV-sensitive security markings on 1996 series