On the third floor, the telegraphy room of clerk Hamdi Bey of Monastır (today Bitola in North Macedonia) is preserved unchanged from those days with all the historical equipment. He was in charge when the Allied troops of World War I (1914–1918) occupied Istanbul on March 16, 1920 following the Armistice of Mudros. He sent messages to Mustafa Kemal (Atatürk) in Ankara using Morse telegraph about the situation in Istanbul until he was stopped by the enemy soldiers, who entered the post office building.