In the mid-1960s, reading and acting on the fine print on a particular class of U.S. paper money meant big profits for thousands of individuals and businesses.

If you were to ask numismatists which denomination of paper money is least useful, nearly all would agree: “the $2 bill.”

Souvenir cards offer an affordable way to collect rare notes such as the Series 1896 silver certificates, better known as the "Educational Notes."