Most British Cruiser tanks from WW2 used the suspension system designed by J Walter Christie with its large road wheels without return rollers as were a number of Russian tank designs the most famous being the BT and T-34 series.
The designations of the early cruiser tanks was rather confusing and changed a number of times within a short period of time.
On the A13 series, there were three types -
A13 Mk I later Cruiser Mk III with the original straight-sided turret and co-axial Vickers machine gun.
A13 Mk II later Cruiser Mk IV with extra armour on the hull front, additional turret armour and co-axial Vickers machine gun, later vehicles had the box over the gun mounting.
A13 Mk IIA later Cruiser Mk IVA had additional hull and turret armour but mounted a co-axial Besa machine gun.
They can be found with two types of gun mounting, the "open" style seen on early Crusaders and Covenanters and the less-common "rectangular" one similar to that on early Daimler armoured cars and Tetrarch light tanks (though it was not the same mounting)
There was a tank confusingly named "A13 Mk III" which was later Cruiser V aka Covenanter but it was a totally different design intended to replace the A13 series alongside the A15 Cruiser VI Crusader.