Ernest Swinton is credited with inventing the terms. To aid steering, a pair of large wheels were added behind the tank. These were not as effective as hoped and were subsequently dropped. The subsequent Mark II, III, IV, and V, and later tanks, all bear a strong resemblance to Mother. Mark I Crew: 8 Combat Weight: 31.4 tons (28.4 tonnes) Armour: 0.23–0.47 in (6–12 mm) Armament: two 6-pounder QF, three Hotchkiss Machine Guns The Gun Carrier Mark I was a separate design, intended to carry a field gun or howitzer that could be fired from the vehicle. In service, it was mostly used for carrying supplies and ammunition. Forty-eight of them were built. Initial production of the Mark I was to be by Fosters and Metropolitan: 25 from Fosters and 75 from Metropolitan, which had greater capacity in Wednesbury at the Old Park site of the Patent Shaft Company, a subsidiary of the Metropolitan. Metropolitan also received an order for a further 50 so that the Army would be able to raise six tank companies of 25 tanks each and set up further production under their Oldbury Wagon and Carriage Company. As there were not enough 6-pounder guns available for all 150 tanks, it was decided to equip half of them with just machine guns. A new sponson design with two Vickers machine guns in rotating shields was produced. Later in the war, when newer tanks came into use, some Mark Is were converted to be used for carrying supplies. A few Female Mark Is were used as mobile wireless stations by installation of a wireless transmitter. The radio could only be operated once the tank had stopped and erected a very tall mast that carried the aerial array. Mark II The Mark II incorporated minor improvements over the Mark I. With the Army declaring the Mark I still insufficiently developed for use, the Mark II (for which orders were first placed in July) would continue to be built, but would be used only for training. Due to this intended role, they were supposedly clad in unhardened steel, though some doubt was cast on this claim in early 1917. Initially, 20 were shipped to France and 25 remained at the training ground at Wool, Dorset in Britain; the remaining five were kept for use as test vehicles. As the promised Mark IV tanks had not arrived by early 1917, it