In 1932, N. Astrov and N. Tsiets completed a prototype of the PT-1 (Plavayushia Tank-1, Amphib Tank-1). The PT-1 was basically an enlarged BT tank hull, large enough to provide enough buoyancy which permitted the tank to float. A propeller was fitted under the hull, and a large rudder was provided for steering. Trials with the PT-1 totalled two years and there was so many problems that it was decided to develop an improved type, the PT-1A. The PT-1A could be distinguished from the early PT-1 by the lack of a side turret and different tracks. None of the prototypes had their armament fitted during trials. The project was considered to be too complicated to enter mass-production and it was dropped. However, a small production run of the PT-1A was completed to permit trials with amphib tanks.