The ZZap D1 has established itself as one of the best selling counterfeit detector pens. The ZZap D1 can instantly verify all currencies. Simply mark any part of the banknote, if the ink turns dark the banknote is likely to be a counterfeit. The D1 is extremely portable and can fit comfortably in your pocket. Ideal for events, taxis, courier drivers, markets etc. The D1 uses iodine-based ink. ZZap has tested various iodine inks to perfect the ZZap D1 so you can be sure you are receiving the best.