Secret messages with this invisible ink pen
This invisible ink pen is ideal to write secret messages anywhere. It really is a marker, but these products are always called pens.
The part that is the cap, has an ultraviolet bulb and a small button that when you press it, the bulb will light up. When you remove the cap, you will see the tip to write that is white and paint with ink that can only be seen if you illuminate what you have written with ultraviolet light.
In addition, it also serves as a fake bill detector. Authentic bills have marks that are only seen with UV light, fake ones do not have those marks.
It works with three button-type batteries that are included, the pen is ready to use.
Who are you going to leave a secret message? :)