The success of the Class NG G13 narrow gauge Garratts that were introduced by the South African Railways (SAR) in 1927 led to a decision that any additional narrow gauge articulated locomotives would be of the same design.
In 1937, Société Anonyme John Cockerill of Seraing in Belgium delivered four new locomotives, numbered in the range from NG85 to NG88, which were so similar to the older locomotives that they were initially designated Class NG G13 as well.