The Cannone da 90/53 was an Italian designed cannon, and one of the most successful anti-aircraft guns to see service during World War II. It was used both in an anti-aircraft role and as an anti-tank gun. The designation "90/53" meant that the gun had a 90 mm caliber and a barrel 53 caliber-lengths long.
Read more about Cannone Da 90/53: History, In Comparison To The German 8.8 Cm, Characteristics