Istanbul Shield (İstanbul Şildi in Turkish) was a soccer tournament which organised between 1930 and 1939. The final match between Galatasaray and Fenerbahçe in 1931 wasn't played. In 1932, Fenerbahçe, Galatasaray and Beşiktaş did not participate and Istanbulspor received the shield. In 1933 the final game was cancelled when Fenerbahçe was leading 2-0. Galatasaray won the repeated game by 1-0 and received the shield.
Fenerbahçe won the trophy for 4 times. The tournament later re-organized with the name "Istanbul Cup" (İstanbul Kupası in Turkish).
References
Istanbul Shield Wikipedia(Text) CC BY-SA