When you hold it up, the light bounces off the grease pen mark and you thought you saw a watermark. In reality, you saw a grease pen mark. If you rubbed it, it would smear. If you turned it over, you wouldn’t see anything. So you have to make sure the watermark is visible, front and back. At the bottom right-hand corner of the bill is the numeral 100, indicating the denomination of the bill. That number is printed in a shiny, sparkly metallic green in what is known as OVI, or optical variable ink. When you tilt the bill slightly forward, the green color of the numeral will turn a dull jet black. Color copiers can’t pick up the changeable appearance of this ink. What’s more, this ink is made by just one company in the world, located in Switzerland, and the ink’s use is tightly restricted. Trying to replicate it is extremely difficult. If the color doesn’t change, you don’t have a real bill. Counterfeiters in the United States use a Revlon metallic nail polish and paint the number in so it’s shiny.
