On their search for a new light infantry tank, the Russian tank designers put their focus on the British Vickers-Armstrong 6-ton E light tank.
In 1930, the first samples arrived in Russia and the own conversion experiments soon started at the Bolshevik factory in Leningrad.
In 1931, 120 of the first series production model, the twin-turreted T-26 Model 1931, were completed.
There were two basic models, the standard T-26 with a DT 7.62mm machine-gun in each turret, and a command tank version, the T-26TU (»Tank Upravleniya«) which had a 37mm gun in the right turret and a DT machine-gun in the left.
A small number of command tanks were fitted with the improved 37mm gun PS-2 Model 1930 which had a longer barrel.
There were plans to equip some with 45mm guns, but this idea was dropped, it being decided to proceed instead with a single-turreted version of the T-26.
Production of the T-26 Model 1931 and its derivatives in 1932 amounted to 1,032 tanks and produc­tion was halted in 1933.
The last batches had welded instead of riveted turrets.

The OT-26, based oh the T-26 Model 1931, originally had a flame projector mounted in the right turret, but because of the need to fit larger fuel tanks in the hull, the left turret was omitted from later models.
The OT-26 was used by chemical tank battalions and the 1935 mechanized corps each had 52 OT-26.
Production probably totalled a few hundred tanks. Source : Zaloga/Grandsen, »Soviet Tanks and Combat Vehicles of WW2«.