https://www.ebay.com/itm/365-nm-3W-UV-LED-Pen-Light-Blacklight-for-Scorpions-Hunting-Mineral-Hunting...Ultraviolet light brings out security features on US and Mexican currency. The alerts fairy SCREAM visually. Simply try it on genuine currency. The pen light clips onto a pocket and 3 seconds of light = many hundreds of verifications. I carry it to town.
I made Brenda a 10 watt UV chip for the restaurant. It is mounted under counter and shines downward. She has caught several 200 and 100 false notes. All from diners from big cities. Obviously they were not the counterfeiters. Most of the time when a moment is given to feel the material of the bill s difference is noted.
I have a phony travel wallet with seven hundred counterfeit bills designed for crooked cops. One motorcycle cop in Monclova snatched a 500 peso bill right out of my fingers.