Tugra of Sultan Osman the Third (1754-1757).
From Enc. Britt.: (tuğra) a kind of royal cipher based on the names and titles of the reigning sultan and worked into a very intricate and beautiful design. A distinctive tuğra was created for each sultan and affixed to imperial decrees by a skilled calligrapher, the neshanı.
I have been informed from several sides that an earlier attribution was wrong.
In addition: It is observed that great viziers, state viziers and seigniories used tuğra-like signatures (called ‘pençe’, which means ‘claw’) in official documents. ‘Pençe’ were written in Arabic letters on over-right, mid or down-side of the document depending on the importance of the subject person. They are seen at left side of the documents in Ottoman documents with western languages. As the difference, a ‘pençe’ include only one curve. Double curves could be only in tuğra.