Day, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1936 to 1939, based on the design of the Class 15E by his predecessor, Allan Griffiths Watson, and later modified again by his successor, M.M.

It was built in five batches by four locomotive manufacturers in Germany and the United Kingdom over a period of ten years spanning World War II.

The locomotive was capable of traversing curves of 275 feet (84 metres) radius with 3⁄4 inch (19 millimetres) gauge widening.

During the 1930s, Day's predecessor as CME, A.G. Watson, designed a standard boiler type as part of his standardisation policy.

[1][9][10][8] The pre-war locomotives were equipped with two large inclined Ross-pop safety valves, mounted on the upper sides of the boiler just ahead of the firebox and aimed about 80 degrees apart.

When these inclined valves blew off under a station canopy, bystanders often received a shower of slimy wet soot.

The weight of the reciprocating parts on each side of the engine was 1,273 pounds (577 kilograms), of which 20% was balanced to ensure that the hammer blow per wheel would not exceed 1 long ton 12 hundredweight (1.6 tonnes) at 55 miles per hour (89 kilometres per hour) and with the overbalance equally divided on all the coupled wheels.

While sources are silent on the reason for the differences, it is known that this engine was oil-fired, although it is not clear whether it was delivered as an oil-burner or modified post-delivery.

His specifications included mechanical stokers, vacuum brakes on the coupled wheels as well as the tenders, with two 24 inches (610 millimetres) diameter brake cylinders on the engine and two 21 inches (533 millimetres) diameter cylinders on the tender, and elephant-ear smoke deflectors instead of smokebox handrails.

[1][2][8][14] The engine's vacuum brake cylinders were fitted outside the main frames under the running boards on each side, between the second and third pairs of coupled wheels.

[1][2] Loubser also modified the leading bogie to have swing links with three-point suspension which eliminated the side control springs that were used on earlier versions.

These engines were delivered with Type ET tenders, which also had a 14 long tons (14.2 tonnes) coal capacity, but a smaller 5,620 imperial gallons (25,500 litres) water capacity to accommodate the mechanical stoker mechanism, while its empty weight was 1,232 pounds (559 kilograms) more due to the additional stoking equipment.

In 1945, the Minister of Transport at the time, the Honourable F. C. Sturrock MP, instructed that a number of Classes 15F and 23 engines should be named after various South African cities and towns and fitted with suitable nameplates in both official languages.

The decorative plates were fitted to the sides of the smokebox or to the elephant ear smoke deflectors of engines which were so equipped.

3030 took the Royal Train on its first leg, departing from Table Bay Harbour's Duncan Dock in Cape Town on 21 February.

[16] On the Western Transvaal System, the Class 15F was for many years the mainstay of mainline steam at Germiston, working to Witbank, Volksrust and Kroonstad.

In 1956 it was decided to temporarily allocate thirty Class GMA Garratts to the Witbank-Germiston section during the transition period from steam to electric working.

On the Midland, several of the locomotives were equipped with chimney cowls from 1960 onwards to ease the smoke nuisance for footplatemen in the many tunnels, but these were of dubious effectiveness.

In later years when the Class 15F was relegated to heavy shunting and local work, many of the locomotives had their mechanical stokers removed.

The outline of a traditional SAR locomotive number plate was used as a commemorative cancellation for De Aar on the date of release.

3007 was returned to its builder's home city, Glasgow in Scotland, where it was initially put on static display in George Square for fundraising purposes by the North British Locomotive Preservation Group.

3007 from staging in the Bloemfontein locomotive depot to Glasgow was recorded in Season 3 of the television documentary series Monster Moves in 2008.

Instead, it was towed by rail on a two-day journey across the country, with ten flat wagons used to augment the braking capacity of the locomotives which hauled the Class 15F.