The Seal of Mindaugas (Lithuanian: Mindaugo antspaudas) is a medieval seal affixed to the October 1255 act by Mindaugas, King of Lithuania, granting Selonia to the Teutonic Knights. An academic debate is ongoing to determine authenticity of the act and the seal as they might have been forged by the Knights. If it is authentic then the seal is the only surviving contemporary depiction of Mindaugas. As the most important surviving artifact from Mindaugas' times, the seal was a centerpiece of a special exhibition organized by the National Museum of Lithuania in 2003 to commemorate the 750th anniversary of Mindaugas' coronation.[1]