From Tampa Police Department District I:

Counterfeiters are bleaching genuine $5 notes and reprinting them as counterfeit $100 notes.

The watermark on genuine $100 bills shows Benjamin Franklin, while the watermark on counterfeit $100 bills shows Abraham Lincoln, instead.

Counterfeit detection pens do not work on this note. To look for the watermark, hold the bill up to the light. The image appears to the right of the portrait and the portraits should match.

If counterfeit notes are detected, please contact U.S. Secret Service Tampa Field Office at (813) 228-2636.