It takes multiple security measures to combat today’s currency counterfeiters. For example, an overt measure would include the numeral twenty on the lower right-hand corner of the new $20 bill. When turned slightly, the numeral shifts color from green to gold.
 
A more “covert” measure might employ use of invisible inks detectable only with a specialized laser reader to determine authenticity. Higher levels of security can involve such features as optical pigments, microprint or magnetic threads.

Sun Chemical Security offers a full range of inks and other products for currency, secure document printing and tax stamps for revenue protection.