ER2 is a DC electric multiple unit which was produced by the Railroad Machinery Plants of Riga (Rīgas Vagonbūves Rūpnīca, RVR) from 1962 to 2003. Since 1960’s ER2 is still a main suburban train of USSR and CIS. The first versions of ER2 were essentially an improvement of the ER1 design, featuring footboards for low platforms, and aprons for high platforms, as well as improved electrical equipment and minor changes to the bodywork (specifically, the engineer’s cab, side walls, headstocks, and door mountings).
ER2-K is almost the same as original ER2. In 2000s in Russia was an issue about modernization of old ER2 trains, and in 2003 by Moscow LRZ there were modernizated a lot of ER2. After modernization they’ve gained prefix “-K”.