In 1963, John F. Kennedy signed an Amendment (11110) to Executive Order No. 10289, concerning the issue of Silver Certificates against Silver bullion. You get a copy of the amendment, a 1935 or 1957 Silver Certificate, and a 1968 Silver Kennedy Half Dollar commemorating this event.

Executive Order 11110 was issued by U.S. President John F. Kennedy on June 4, 1963. 

This executive order amended Executive Order 10289 (dated September 17, 1951) by delegating to the Secretary of the Treasury the president's authority to issue silver certificates under the Thomas Amendment of the Agricultural Adjustment Act, as amended by the Gold Reserve Act. The order allowed the Secretary to issue silver certificates, if any were needed, during the transition period under President Kennedy's plan to eliminate Silver Certificates and use Federal Reserve Notes.