The British 3.7in AA gun

The Official History mentions the British 3.7in AA gun. The primary role of this gun was heavy AA, and the guns were positioned guarding major installations such as the Suez Canal, as well as landing grounds. The gun was capable of being used in the anti-tank role, when supplied with a suitable gunsight. Finally, in April 1942, sixty 3.7in AA guns were fitted for the anti-tank role. A very few were used in a portion of the abortive Gazala battle in May. This is based on a note in Vol.III of the Official History. Contributors have increasingly made the Wikipedia a good source for information about tanks and guns. There is a page for the "QF 3.7in AA Gun".