Inscription: Constantinople arsenal
"Some European specialists are of the opinion that it indicates swords of Ottoman make, but we meet the same mark on those of Memlûk and Iranian make. In the Selçukname and the Hünername, chronicles of the Selçuk and Ottoman periods resepectively, are described in detail, and reproduced in drawing the crests and marks used by the different Turkish tribes. The above mark belonged to the Oguz tribe, and their crest was a falcon. The Hünername tells us that the Ottoman Turks, being of Oguz descent, adopted the aforesaid mark, and it was used likewise in the Imperial Mews'. It appears therefore that all arms, whether made in Turkey or any other country, on passing into the possession of an Ottoman Sultan were impresses with this mark."
This markpasses as (or is thought to be) the Tamgha (seal) of the Sultan Mohammed II called the Conqueror (1451-1481 AD).