Girouard KCMG DSO RE, the Commissioner of Railways for the Transvaal and Orange River Colony, therefore placed urgent orders for 35 locomotives of the NGR's Reid Tenwheeler type.

The locomotives were more ornate than those in Natal and, in true military style, their brass domes, chimney caps and boiler bands were polished.

[1] The Royal Engineer officers of the IMR considered the Reid Tenwheeler as an excellent and handy type of locomotive for the heavy gradients of 1 in 100 (1%) to 1 in 50 (2%).

[1][3][5] From c. 1903, six locomotives, numbers 222, 233 to 235, 245 and 252, were converted to 4-8-2T Mountain type engines by removing the fifth pair of coupled wheels and blanking off the resulting opening in the frame, similar to the modification which was being done by the NGR on its own Reid Tenwheelers to make them better suited for the tight curves encountered on points during yard working.

[1][2] Since the small coal and water capacity of the Reid Tenwheelers limited their radius of action, one of them was converted to a tank-and-tender configuration in 1904.

As a result, the remaining 28 unmodified Reid Tenwheelers were similarly modified to the 4-8-0TT Mastodon type configuration, using three-axle tenders from CSAR Class 6-L2 locomotives.