The Australian Cruiser tank Mark 1 (AC1) was designated "Sentinel" in February 1942. Fabrication was by Sydney's Chullora Tank Assembly Shops with serial production vehicles emerging in August 1942, the premises also being used as a testing ground. The design used existing parts where available from other tank designs, simplified where necessary to match the machining capacity present in Australia. The hull was cast as a single piece, as was the turret; a technique not used on the hull of any other tanks of the era.(rudeerude)

Australian "Sentinel"

Original caption: "25-pounder guns of the 2/8th Field Regiment, Royal Australian Artillery, in action on the coastal sector near El Alamein, Egypt. They are being fired at a range of 9,800 yards on to enemy positions. As a reprisal shoot this troop fired 1,250 rounds in one and a half hours at rapidly changing ranges in reply to German artillery which fired 700 rounds in one hour. A pile of empty shell cases is seen in foreground."

Date: 12 July 1942, during the First Battle of El Alamein

25-Pounder Guns, 2/8th Field Regiment

A variant of the "Sentinel", AC IV with a 17 pounder.