The two Mountain types, which arrived from the same builders in the same shipment, were designated Class 15C. The Classes 16D and 15C were specially designed for working the Union Limited (Johannesburg to Cape Town) and Union Express (Cape Town to Johannesburg) passenger trains, the forerunners of the Blue Train.Soul of A Railway, System 7, Western Transvaal, based in Johannesburg, Part 1. Johannesburg between the Home Signals, Part 1. Caption 18. (Accessed on 20 March 2017)
