This one dollar bank note was originally backed by silver that was deposited in the United States Treasury and, until June 24, 1968, it could be redeemed for the actual silver. The blue Treasury seal on the front identifies it as a Silver Certificate. It has been signed on the front by Sonny Liston and Joe Louis. Cassius Clay (Muhammad Ali) signed the back of the bill. All fighters autographed in blue ballpoint pen. PSA/DNA certified authentic.