Close examination of a considerable number of photographs of Mark III tanks, together
with those available for examination in the Western Desert, indicates that
the Mark III fighting-type tank is found in three basic designs.
Of these, the first has an armor basis of 30 mm (1.18 in) all around. The
front sprocket has eight spokes, and the rear idler, though having eight spokes, is
almost solid. This type is known originally to have been produced mounting a
37-mm gun and either one or two machine guns coaxially in the turret, with one
machine gun firing forward in the hull. Later, however, the 50-mm was substituted
for the original principal armament, and this mounting has only one machine gun
mounted coaxially in the turret, the hull machine gun being retained. Of the
actual specimens examined, all mounted the 50-mm gun (many are now mounting
the long-barrelled type), and in these there has invariably been a Variorex
gearbox, the steering being hydraulically operated. This basic type, irrespective
of armament, has not been found to carry any additional armor, improvised or otherwise.
The second type has an armor basis of 30 mm all around with additional
30-mm plates bolted on. This type has a six-spoke front sprocket, and the rear
idler, although having eight spokes, is more open than the first type. An
ordinary six-speed gear box and hydraulically operated steering gear are
fitted. Neither photographs nor specimens of this type have shown any principal
armament other than the 50-mm gun with one coaxial machine gun. Moreover, every
individual tank of this type has had similar additional 30-mm plates on the front
and rear, this additional armor not having been found on any other type of
Mark III fighting tank. The inference is, therefore, that this additional
armor is actually part of the design of the tank and probably incorporated
during manufacture. There have been no indications that this type originally
mounted a 37-mm gun, although this remains a possibility.
The third type has 50-mm armor on the front and rear, with 30-mm armor on the
sides. No additional armor has been found on any tanks of this type, and the
armament has always been found to be the 50-mm gun with a coaxial machine gun
and one machine gun in the hull. The front sprocket and rear idler are similar to
those in the second type, and an ordinary six-speed gear box is fitted, the steering
being operated by mechanical linkage. The driver's and hull gunner's entrance
doors have been changed from the former double doors to single doors hinged
at the forward edge. In place of the normal mantlet protecting the hull
machine gun, a more hemispherical mantlet is fitted.
The following minor differences of design between these three basic
types have also been noted. Originally on the first type the armor protecting
the driver's visor consisted of two plates, one being raised, and the other
lowered, to give protection. The third type, and probably the second type as
well, have had a single hinged piece of armor which can be lowered to give
protection. The third type has also had a slightly different design of the
two shields protecting the exhausts from the steering tracks. In the first
and second types the air filters were located between the rear bulkhead of
the fighting compartment and the engine, air being drawn from the fighting
compartment. These filters were believed to be an oil-soaked gauze type. On
the third type this arrangement superseded by four oil bath filters, installed
over the top of the engine blocks.
The suspension on all these types has been the same, the familiar six small
bogie wheels with three return rollers, a front sprocket, and a rear idler. Two
early types, however, are known to have had respectively five large bogie
wheels and eight small bogie wheels. Both these types mounted a 37-mm gun. Nothing
has been heard of either type over a considerable period, and it is probable that
they were prototypes only and not produced in significant numbers.
It is known that Mark III fighting tanks have been produced in at least
five models designated 'E', 'F', 'G , 'H', and 'J.' These models have consecutive
chassis number blocks, and it is logical to assume that they are successive
developments. There should therefore be a link with the development shown
above, but so far it is not possible definitely to say what each model designation
represents. It is, however, known that the first type described above has
included Model 'G' tanks, and the third type has included Model 'J' tanks. All three
types are known to have been in existence early in 1941, the third type probably
being at that time a very new production.
It should be specially noted that, in describing German armor thickness, round
numbers are almost invariably given. Careful measurement, has shown that these
figures are frequently incorrect. 30-mm, for example, should almost invariably
be up to 32-mm.