Notes: The first steam, class 2-10-2, was built at the Lugansk works at the end of 1931. To memorise the name of the Russian revolutioner Felix Dzherzinskiy it was named after him FD-20 (the number "20" denominates the maximum axle weight). In the period 1931-1940 the steam loco FD-20 was the main freight loco at the USSR railways. The modified version of this class was named FD-21. During the period 1932-1941 the Lugansk works built FD20 - 2925, FD21-286. During the WW2 in 1942 the production of the last 4 steam locos of this class was finished at the Ulan-Ude works. Since 1945 the most steam locos were reconstructed into the oil version, with the stoker removed, with a new index N, FDn. By the middle of the 60-s they were actively taken off the operation. In 1958-60 950 broad gauge steam locos of this class were rebuilt into the 1435 mm-gauge and transferred to the Chinese railways for the freight traction.
