[1][2][3] Type XS tenders were built in 1911 by the American Locomotive Company (ALCO).

[1][2][3] In 1911, the Central South African Railways (CSAR) placed nine 2-6-6-2 Mallet articulated compound steam locomotives in service, built by ALCO.

These locomotives were designated Class MF on the South African Railways (SAR) in 1912.

[1][2][3] The tender had a coal capacity of 10 long tons (10.2 tonnes), a water capacity of 5,000 imperial gallons (22,700 litres) and an average maximum axle load of 13 long tons 16 hundredweight (14,020 kilograms).

[3][4] Only the first batch of nine Class MF locomotives of 1911 were delivered new with Type XS tenders.