On the picture: Some details of the monumental gate of the Ayasofya Ímareti (soup kitchen for the poor), which sultan Mahmud I (1730-1754) had built adjacent to the Ayasofya complex (at its northeast corner, to be precise) in 1743. The calligraphy is the ‘tuğra’ of Mahmud I.
A ‘tuğra’: a calligraphic monogram, seal or signature of an Ottoman sultan, that was affixed to all official documents and correspondence. It was also carved on his seal and stamped on the coins minted during his reign. Each sultan generally chose the precise form of his ‘tuğra’ on the day of his accession from specimens prepared for him in advance by the court calligrapher. The first ‘tuğra’ belonged to Orhan I (1284–1359), the second ruler of the Ottoman Empire and it evolved until it reached the classical form in the ‘tuğra’ of Sultan Suleiman the Magnificent (1494–1566).
Correspondent: J.M.Criel, Antwerpen.
Source: Website of ‘ayasofyamuzesi.gov.tr’ & Wikipedia.