In July 1941 the US Army Ordnance Corps issued specifications for a heavy armored car (along with another specification for a medium armored car, which resulted in the T17 Armored Car) to be built for supply to the British. The prototype was developed in 1942 by the Yellow Coach Company. It was large 8x8 (eight wheels, all driven; called an "eight-by-eight") vehicle with four front wheels used for steering. Thick armor brought the weight to 26 tons, about the weight of contemporary medium tanks. Initial armament consisted of a 37 mm gun M6 in a turret with a coaxial .30 inch machine gun and another .30 inch MG in the bow mount. By then it was clear that the anti-tank performance of the 37 mm gun was insufficient and the production version, the T18E2, which was named Boarhound by the British received the 57 mm gun M1, the US-manufactured variant of the British QF 6 pounder. The United States Army had never shown interest in the vehicle. The British Army placed an order for 2,500 units, but high production costs and poor cross-country performance led to cancellation of the order after only 30 were delivered.