Counterfeit Bill Detector Pens Suitable for Most Currencies Our counterfeit detector markers are suitable for most currencies. They can be used for United States Dollar (USD), Euro (EUR), British Pound (GBP), and many other types of currency. Durable Our pens come with a chisel tip to extend the life of the marker. Keeping the pen with the cap on will allow you to use it for a long time by preventing the ink from drying out. Portable Size With dimensions similar to a pen or pencil, you can take this counterfeit pen on-the-go and instantly verify if your bills are genuine. Easy to Use All you need to do is mark the banknote and in less than 2 seconds you will know whether it is a suspicious bill. When marking a genuine banknote the mark will become clear or yellowish. If the banknote is not genuine, the mark will turn dark brown/black.