The flag of the Ottoman Empire.Unknown year and purpose of use.But it is expected to be used for war flags.Written Bismillah and Surah Al-Fath verse 1 in Arabic script.
https://i.pinimg.com/originals/1a/28/3a/1a283a203b813d97bc6d7f891089f0fa.jpg
https://pin.it/52rOUhT

Bismillah written by Khattat 'Uthman At-Tooni,Qahirah (Cairo),Egypt from Ajmal Namazij Wal Takwinaat Az-Zukhrufiah Fi Fann Kitaabah Al Basmalah (Ahmad Sabri Zaid,Darut Thala',Cairo)
Ottoman Sultanate