Designed for anti-aircraft defence, the 3.7-inch MK III gun first came into service with the Commonwealth Armies in 1937. They later saw use during World War II and served in the Middle East, Europe, and the Far East.
A radar and predictor continually followed the target, computing its future position for the gun. The gun could also fire on ground targets with the addition of a scope sight.
Positioned about five miles out from Hobsonville and Whenuapai, the gun was employed in the anti-aircraft defence of Auckland in 1942. The defence area included Auckland's two air force bases and the Navy base at Devonport. It was later converted to a mobile Coast Defence gun.
With the advent of high-speed aircraft and guided missiles in the late 1950s, these guns have now become obsolete.
Specifications
| Crew | Nine | |
| Weight | 9 tonnes | |
| Muzzle Velocity | 813 m/sec | |
| Range Height | 12,000 metres | |
| Range Horizontal | 18,800 metres | |
| Bore | 3.7 inch | |
| Shell weight | 28 lbs | |
| Rounds per min | 20 automatic / 15 manual | |
| Manufactured | England |
