Since 1968 they have been redeemable only in Federal Reserve Notes and are thus obsolete, but still valid legal tender at their face value and thus are still an accepted form of currency. In 1928, all United States bank notes were re-designed and the size reduced. The complete type set below is part of the National Numismatic Collection at the Smithsonian's National Museum of American History. Certificate of Authenticity - Calhoun's Collectors Society.