They first entered service in 1912, as tenders to the SAR Class MC 2-6-6-0 Denver type Mallet locomotive.

[1][2][3] Type TM tenders were built between 1910 and 1912 by the North British Locomotive Company (NBL).

[3] The tender had a coal capacity of 8 long tons 5 hundredweight (8.4 tonnes) and a water capacity of 4,000 imperial gallons (18,200 litres), with a maximum axle load of 10 long tons 18 hundredweight (11,070 kilograms).

The first letter of the tender type indicates the classes of engines to which it could be coupled.

[3] A number, when added after the letter code, indicates differences between similar tender types such as function, wheelbase or coal bunker capacity.