1958 - 1972
On July 12, 1958, just in 100 working days after the last RSM-8 harvester left the main conveyor, the accepting authority of Ministry of Agriculture accepted the first 27 self-propelled harvesters produced by Rostselmash and designed by Taganrog Design Bureau under the leadership of Isacson.
On January 24, 1961, the SK-3 self-propelled harvester number 100000 was produced.
In February, 1962, Rostselmash started production of the next serial model SK-4, which exceeded the previous one by 25% in respect of efficiency.
In 1963, the machine was awarded I-grade diploma at international exhibition in Leipzig, and, in 1964, the model was awarded a medal in Czechoslovakia, and, in the same year, it was awarded with a highest award Silver Cup in Hungary. The SK-4 harvester has been acknowledged as the awarded model among grain harvesters all over the world.