The original Class 15C, built by Baldwin, was the first of two practically identical classes later classified 15CB and 15CA. The first pair of 15C's were supplied together with two 16D Pacifics, as trial of large American type locomotives for South African conditions. Their success led to the purchase of 10 further 15C's.

The next order for 15C's was built by ALCO with a modified frame arrangement at the rear end in which a bridle casting was provided in front of the firebox, this having been an area of frame weakness on the Baldwin engines. When the ALCO engines were delivered they were classified 15CA and the earlier Baldwin engines 15CB.

During the regime of CME Watson, both classes were fitted with wheels and cylinders three- and one-inch larger diameter respectively, roughly comparable with the 15E and 15F classes. However, they are hand fired and have smaller boilers and are therefore not capable of the sustained hard work of the later classes.

At first these engines worked between Cape Town and Kimberley and also in the Orange Free State. In later years the entire class was transferred to the Transvaal and worked on the lines radiating from Pretoria. In the 1970's one batch was sent to Natal and worked on the North Coast line and later at Pietermaritzburg on shunting duties.

However, the remaining examples were all sent back to the Transvaal. The 15CB's were all withdrawn during the 1970's but perhaps not surprisingly were snapped up by industrial systems. Except for No.2060 retained for the Transnet Museum all were still in industrial use in 1990. However, the 15CA's have remained reliable engines and around 12 are still in service on hire to mines in the Transvaal. These engines are popular with enthusiasts and are renowned for their extremely crisp bark, the loudest of all the SAR steam locomotives. 15CA No. 2054 'Cheeta' is now based at Dal Josafat.