The few Sentinels that were built never saw action as Australia's armoured divisions had been equipped by that time with British and American tanks.

[2] When design work began in November 1940, the AC1 was originally intended to be a 2 pounder gun-equipped vehicle, a true Cruiser tank,[3] with a weight of between 16 and 20 tonnes.

Watson MC, an artillery officer with many years of tank design experience was provided by the UK.

[8] Manufactured by the New South Wales Railway Company,[4] fabrication took place at Sydney's Chullora Tank Assembly Shops with serial production vehicles emerging in August 1942, the premises also being used as a testing ground.

The AC2 was a modified Sentinel with thinner armor and a less powerful engine that was designed to be simple and quick to produce.

However, the Australian Army deemed the armor and speed of the AC2 lackluster compared to preexisting contemporary tanks, and the government did not want to take resources away from the ongoing AC1 Sentinel project at the time.

[16] The Sentinel was to be succeeded by the AC3 Thunderbolt, a much improved design with better armour protection, and most importantly increased firepower.

[20][21][Note 1] The 65 tanks that were not required to serve as a physical record in war museums in Australia and the UK were sold off by the Commonwealth Disposals Commission.

This tank, acquired from the MTM, has a largely uncut hull, with turret, gearbox and running gear, otherwise bare inside.

[24] An AC3 mockup was assembled from unused AC3 armour castings and a mix of AC3 and AC1 parts at the Melbourne Tank Museum in 1996–97, this piece was sold to a private collector in 2006.