Mike writes: Here is a scan of a twenty dollar bill I found (1996) and the Watermark is on the outside and can be seen with out holding it up to the light, both sides. Why is that?
This is a genuine FRN. It looks as if someone stained the paper either by accident or intentionally to see the watermark. Watermarks aren’t part of the printing process, they are part of the manufacture of the paper. This is not a printing error.