Late-Ottoman ‘Turkish Baroque’ style. The fountain is located to the right of the Dolmabahçe Mosque, along the Bophorus at Kabataş. The calligraphic inscription is dated 1317 H. (= 1899-1900 AD).
On top of the fountain stands the ‘tuğra’ of Abdülhamid II (1876-1909).

A ‘tuğra’ is a calligraphic monogram, seal or signature of an Ottoman sultan, that was affixed to all official documents and correspondence.

Correspondent: J.M.Criel, Antwerpen.
Sources: (amongst others) Vikipedia/Wikipedia & Website of ‘eskiistanbul.net’.

The first time I took its picture it was freestanding, now it is so close to the Kabatash ferries that it's almost surrounded by people, stalls et cetera.