This one is dated 1962 and is ex British army which fits nicely as the guns supplied to the

Anzac forces came from the British army and not the Italian manufacturer.The L5 Pack Howitzer was designed and built in Italy by OTO Mellara and was originally known as the Model 56. Specifications for the design stated the requirement for it to be fully transportable throughout the mountainous regions of Italy and Europe. Hence the pneumatic tyres for high speed towing and the ability for it to be dismantled into 12 sections for transport across rough terrain.  The weapon was, in fact, light enough to be carried slung underneath the Bell UH1 Iroquois helicopter.
Original production began in 1957 and was soon adopted by many countries throughout the world. Production ceased in 1984 with some 4200 weapons delivered. The weapon has seen action in many combat areas, including by the British in South Yeman and Borneo, Australia and New Zealand in South Vietnam with Argentina using the weapon in the 1982 Falklands campaign.
The L5 has a very short barrel with a multi baffle muzzle brake, a hydraulic buffer and helical recuperator and a vertical sliding wedge breech block. The weapon’s normal crew was seven men and was towable by a long wheelbase Landrover. An advantage of the L5 was that it fired the same 105mm ammunition as the American M101 and M102 field guns.
This type of ammunition was manufactured world-wide and included High Explosive (HE), smoke, illumination and High Explosive Anti Tank (HEAT).
A modification developed during the Vietnam conflict was the Flechette round, designed for local defence, in which a round fired at close range exploded shortly after leaving the barrel, sending out thousands of 2″ finned steel darts. The maximum range, at full charge, was 10575m or 11565 yards.