The 20mm quad AA Tank, Skink, was the most successful attempt to mount an anti-aircraft gun on the chassis of a Sherman tank, but only a handful were produced, and their main use was against ground targets.
The requirement for a self-propelled anti-aircraft weapon was issued by the Canadian Department of National Defence in the autumn of 1943, for use in the upcoming invasion of Europe. The new vehicle was to carry four 20mm guns, and be based around the Grizzly Tank, a Canadian produced version of the M4A1 Sherman.
The new weapon was developed by the Waterloo Manufacturing Company. The first specification called for four 20mm Hispano-Suiza guns. Waterloo produced a wooden mock-up and a steel turret to carry these guns, but the specification was then chanced to four 20mm Polsten cannon.
The new turret was carried on top of a standard Canadian Grizzly. Both the turret traverse and gun elevation used Oilgear hydraulic drives. Ammo for the 20mm guns were carried in sponson racks, which held sixty four 30 round magazines. The Skink carried a crew of five, with three in the turret. The gunner sat between the two pairs of guns, with the loader at the rear left and commander at the rear right of the turret.
The Skink was accepted for production, and work began at the Montreal Locomotive Works in January 1944. By this point it was clear that the Allied air forces had won air supremacy over Europe, and the anti-aircraft vehicle was no longer needed. Production ended after three complete Skinks and eight conversion kits had been completed.
One Skink was tested in combat by the First Canadian Army in February-March 1945. By this point the Luftwaffe was almost entirely absent, but it did prove to be useful against ground targets, and especially against German infantry positions.