In 1900 the British War Office placed two Sirdar class 0-4-0T tank steam locomotives in service on a narrow gauge line near Germiston in the "Zuid-Afrikaansche Republiek", where the Royal Engineers had established a siege park during the Second Boer War. The locomotives were built by Kerr, Stuart and Company. At the end of the war, the two Sirdar locomotives were sold to a farmer, who used them on a firewood line between Pienaarsrivier and Pankop, until the line and locomotives were taken over by the Central South African Railways (CSAR). In 1912, when these locomotives were assimilated into the SAR, they were renumbered with an "NG" prefix to their numbers. When a system of grouping narrow gauge locomotives into classes was eventually introduced by the SAR somewhere between 1928 and 1930, they were designated .