The U.S. Postal Inspection Service is offering a reward of up to $50,000 for information leading to the arrest and conviction of the people responsible.

The limited-edition stamp, unveiled today at the Newseum by actress Gabrielle Union and Rep. John Lewis, features an illustration of a group of marchers holding signs that say “We Demand Equal Rights Now!” and “We March For Jobs For All Now!”

The United States Postal Service will announce Wednesday that it is ending Saturday mail delivery effective August 1, in a move the cash-strapped agency hopes will offset some of the bleeding.