(The following is a post by Joan Weeks, Head of the Near East Section and Turkic World Area Specialist, African and Middle Eastern Division.)
From the inception of the Ottoman Empire in 1299, until its dissolution in 1922, the sultans from the House of Osman ruled the Ottoman dynasty in direct succession. The second ruler Sultan Orhan I (1288-1360) was the first to have a tughra designed as a calligraphic monogram or signature that would be affixed to all official documents. Later sultans also had their tughra stamped on coins minted during their reign.