The Seal of Mindaugas () 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. Act and seal During an internal struggle in 1250, Mindaugas allied himself with the Livonian Order and the Teutonic Knights. With Orders' assistance he defeated his enemies, converted to Christianity, and was crowned as King of Lithuania in 1253. For their help, Mindaugas granted various lands to the Knights in 1253, 1255, 1257, 1259, 1260, and 1261. These six acts caused much controversy and debate among modern historians regarding their authenticity. Only one act, the October 1255 act concerning Selonia, survives with a seal of Mindaugas. The Selonian act was mentioned by Pope Alexander IV in a papal bull, dated July 13, 1257, confirming the territorial transfer. A transcript and detailed description of the seal was made in May 1393 by a papal legate. The 1393 description is an accurate representation of the surviving seal except for the string holding the seal to the parchment: according to the description the string was white and yellow while it is now white and blue. The original document is preserved by the Prussian Privy State Archives. The seal is about in diameter (the exact size is impossible to determine because its edges have chipped off). It depicts a ruler sitting on a bench, covered by a cushion or drapery. The ruler wears a royal mantle and a crown. The right arm holds a scepter decorated with a large lily, while the left arms holds an orb with a cross. The empty field around the figure is decorated with a Gothic diamond-shaped latticework. The diamonds have a tiny cross in the middle of them. The legend where Mindaugas' name and title should appear is almost completely chipped off. The only surviving details are a tiny cross, which would indicate the beginning of the legend's text, and a letter. The letter was variously read as M,