In 1882 and 1883, the Cape Government Railways placed 68 4th Class 4-6-0 tank-and-tender locomotives in mainline service on all three its systems.

On the Eastern System, problems were experienced with the low-grade local coal from the Cyphergat and Molteno collieries in the Stormberg.

[1][3] John D. Tilney, the Eastern System Locomotive Superintendent, carried out many experiments in an attempt to overcome the coal problem.

[1] Another modification by Tilney was an extended smokebox to make room for a very efficient spark arrester which was constructed of wire mesh.

In 1881, the General Manager appointed Hawthorne R. Thornton as Chief Locomotive Superintendent for the whole of the Cape of Good Hope in response to the "growing tendency on the part of the several Locomotive Superintendents to bring in modifications of designs in essential parts of the engines and rolling stock".

The increased amount of exhaust gases present in the smokebox had the effect of stabilising and improving the draught.

The date of this improvement can be pinned to 1891 when the second batch of Michael Stephens’ Cape Government Railways (CGR) 5th Class 4-6-0 locomotives with their lengthened smokeboxes entered service.

This had such a profound effect on the boiler’s steaming ability that virtually every locomotive on the CGR and NGR had their smokeboxes extended.

[6] While the locomotives proved to be good all-purpose engines, the Joy valve gear was not considered entirely satisfactory.

[2][7] At the time these 4th Class locomotives entered service in 1882, the two Eastern System mainlines were open to King William's Town and approaching Sterkstroom respectively.

They were considered obsolete by the South African Railways, designated Class 04 and renumbered by having the numeral "0" prefixed to their existing numbers.

[1][9] In 1915, shortly after the outbreak of the First World War, the German South West Africa colony was occupied by the Union Defence Forces.