 During the 1950s NOHAB of Trollhättan had started a cooperation with General Motors Electro-Motive Division to licence build GM-EMD diesel locomotives for the European market.SJ had bought one EMD G12 locomotive, retrospectively designated T42, in 1953 and after NOHAB had started building the DSB class MY and MX for Danske Statsbaner in 1953 SJ ordered five modified G12 locomotives in 1955 with delivery in 1956.It had six axles and a GM EMD 567C prime mover, but with a central cab.