Flag of Siluana (Transylvania), around 1350, according to the story of a Spanish Franciscan friar: 

From Maxar I went to the Kingdom of Siluana, which they call Septen Castra, and the Greeks call it Horgiml (Transylvania). It is encircled by two great rivers — the Turbo (Dniester) and the Lusim (Dnieper). The king has for his device a green flag with a red scimitar. The people are schismatic Christians.
self made after National Geographic, October 1917 issue.
Alex:D