On March 25, 1931, the U.S. Armaments Department and the U.S. Wheel Track Layer Corporation led by John W. Christie signed a contract to develop five wheeled caterpillar tanks. In three months, that number increased to seven. The production vehicle was based on the Convertible Medium Tank M1931 prototype that failed testing in early 1931 on Aberdeen Proving Ground and was later sold to the U.K. Three of the seven vehicles were named Convertible Medium Tank T3 and were used by the infantry, and the remaining four, named Combat Car T1, went to the cavalry. The tanks saw service until 1937. Only one vehicle has survived to this day.