When these two locomotives were assimilated into the South African Railways (SAR) in 1912, they were renumbered 604 and 605 and designated Class 6F [REF].
The rest of the CGR's 6th Class locomotives, together with 6th Class locomotives which had been inherited from the Oranje-Vrijstaat Gouwerment-Spoorwegen (OVGS) via the Imperial Military Railways (IMR) and the Central South African Railways (CSAR), were grouped into thirteen more sub-classes by the SAR.