Former Soviet Railways Да20-09 (Da20-09) on exhibit at the railway museum in former Varshavsky terminal -- Saint Petersburg, Russia. Originally built by ALCO as a model RSD-1 in 1944 and exported to the USSR.
The ALCO RSD-1 was a diesel-electric locomotive built by American Locomotive Company (ALCO). This model was a road switcher type rated at 1,000 horsepower (750 kW) and rode on three-axle trucks, having a C-C wheel arrangement. It was often used in much the same manner as its four-axle counterpart, the ALCO RS-1, though the six-motor design allowed better tractive effort at lower speeds, as well as a lower weight-per-axle. It was developed to meet the Soviet demands of a locomotive with a lower axle load. On the other hand, due to the traction generator and appurtenant control apparatus being sized for four axles and yet having two additional powered axles, it had poorer performance at higher speeds.
There were three different specifications issued that covered the RSD-1 model; E1645 and E1646 were for wartime production for the US Army, while E1647 was a post-war order for the Mexican National Railways (Ferrocarriles Nacionales de México).
Seventy of the RSD-1s were shipped overseas to the Soviet Union in 1945 during World War II, as part of the Allied war effort. They were classed there as the Soviet Railways Да20 (Da20) class, also known after 1947 just as ДА (D for Diesel, A for Alco and 20 for axle load in tons). These locomotives were also used on the Trans-Iranian Railway. The Soviets subsequently kept many of the RSD-1s after the war, adopting the design to form the basis of their own line of diesel locomotives TE1, TEM1 and TEM2. A dozen RSD-1s were sunk en route to the Soviet Union when the ship they were on was torpedoed by a German U-boat. According to Russian sources, 68 RSD-1 were received, and only two (Да20-41 and Да20-50) sunk on the way. Some were still in service in the 1980s.
The Soviet-built TE1 (ТЭ1) was almost identical to the Alco product but locomotives after #TE1-20-122 had 41.5 inch, instead of 40 inch wheels. The TE2 (ТЭ2) was a twin-unit version of the TE1. The TE5 (ТЭ5) was a cold climate version of the TE1. The cab was extended to provide covered access to the engine inspection doors and a boiler was added to keep the cab warm when the engine was not running. 
The first 13 RS-1s were requisitioned by the US Army, returned to ALCO and rebuilt to RSD-1s #8000-8012 for use on the Trans Iranian Railroad. This effort was to supply the Soviet Union. See the RS-1 article for the identity of the first 13 RSD-1s.