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The Canadian "Skink" was undoubtedly the most effective and successful wartime anti-aircraft design based on the chassis of the American M4 Medium tank. The need for such a tank was recognized in 1943 as the imminent invasion of North-West Europe approached. Its primary role was envisioned to be in defending armoured columns against Luftwaffe strafing attacks, and secondarlily; in a ground support role against softskin targets.

The pilot model was constructed at the Waterloo Manufacturing Company. It was based on the Canadian produced M4A1 "Grizzly I" hull and chassis, mounting a special turret armed with four 20mm Hispano Suiza cannons. A wooden mock-up and a steel pilot turret were constructed before the specifications were changed. The Hispano Suiza guns were replaced with Polsten 20mm Mk. I cannons. The change necessitated the gun mount being completely redesigned to accomodate the Polsten guns.

Initially, a welded turret had been considered as it proved difficult to acquire a cast turret possessing accurate balance, while still maintaining the required ballistic properties. Eventually, the problem was solved and a one-piece cast turret was selected for production. It had four individual gun cradles and mantlets; all of which were linked in parallel to a pair of hydraulic elevating rams. The turret was capable of 360° traverse and the turret crew consisted of the commander, gunner and loader. Both the commander and loader were stationed in the rear of the turret with the gunner located forward, between the guns. Each crew member had his own hatch. Late production turrets had a distinctive rear undercut and a clearance bump inside each of the sighting hatches.

The Polsten cannons could be elevated to +80° and depressed to -5°. The guns could be fired simultaneously, individually, or in banks of two. They were fed by 30 round magazines which were replaceable within approximately 20 seconds. A total of 64 magazines holding 1,920 rounds were stowed in the tank. The gunner sighted the cannons with the "Sight Illuminated, Mk. IX (U.S. Navy) Model "O", 24-volt", which was carried on a mount that moved with the guns. Unfortunately, this sight required that the driver expose his head from the confines of the turret when firing in an anti-aircraft role. When engaging ground targets however, he could remain under cover and sight by means of observed tracer fire. The Skink used HEIT (High Explosive Incendiary Tracer) ammunition when engaging ground targets.

The gunner's handle bar controls incorporated finger buttons with which to fire the Polstens. In this arrangement, each grip had a button; the right button to fire the upper guns and the left button to fire the lower ones. Traversing the turret and elevating the guns involved the use of "Oil Gear" pumps. These pumps incorporated control cams, which were driven from a common electric motor to provide hydraulic power. The gunner simply pushed down on one of his hand grips to rotate the control column on a vertical axis. The speed the turret traversed depended on how much the grip was moved. The turret could rotate at a maximum of 10 revolutions per minute. To accomplish such speed, a modified engine driven generator was required, plus the installation of a newly developed high output auxiliary generator.

In all, only three complete Skinks were produced, in addition to eight complete turret kits for installation on existing Grizzly I chassis'. Production commenced in January 1944 and was suspended when it became apparent that Allied air supremacy in North-west Europe eliminated the need for anti-aircraft tanks.

A Skink underwent firing trial evaluation at the Experimental Wing AFVG School, Lulworth, England in January 1945, with No. 1 Tank Demonstration Unit, Canadian Armoured Corps. The report commented favourably on the general turret, gun and ammunition storage layouts, and the ability to engage targets without the use of the main engine. It noted though, that there were high creep speeds and a lag in response time in the gunnery controls.

In February-March 1945, the Skink underwent user trials with armoured regiments in 1st Canadian Army, in North-West Europe. It was considered to be a great improvement over the Crusader AA tanks which had been in use up to then. It was used in a ground support role where it advanced with the second wave of armour to clean out infantry positions that had been by-passed by the first wave.

Although the Skink was an excellent anti-aircraft platform, the need for such a tank was all but eliminated as Allied air superiority in North-West Europe had cleared the skies of any potential Luftwaffe threat. Sadly, there are no surviving examples of this unique tank but one turret did survive on the Range at CFB Shilo where it was used for gunnery practice.