The NZASM 19 Tonner 0-4-2T of 1891 was a South African steam locomotive from the pre-Union era in Transvaal.

In 1891 and 1892, the Nederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij of the Zuid-Afrikaansche Republiek (Transvaal Republic) placed 24 tank locomotives with a 0-4-2 wheel arrangement in service.

[1][2] Between 1906 and 1909, ten of them were converted to railmotor engines by the Central South African Railways, for use on suburban passenger services.

[3][4][5] The first ten of eventually twenty-four tank locomotives with a 0-4-2 wheel arrangement, built in two batches of five by Emil Kessler's Maschinenfabrik Esslingen in 1890, were placed in service by the Nederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij (NZASM) in 1891 and numbered in the range from 21 to 30.

The cylinders were arranged outside the frames, with flat Murdoch's D slide valves arranged at an incline above the cylinders and actuated by Allan straight link valve gear, driven by eccentric sheaves which were mounted on a return crank.

[1][2] At the time the 19 Tonners entered service, the Randtram line and the extensions towards the east to Springs and towards the west to Roodepoort were open.

[6][7] At the end of the war, when the IMR was transformed into the Central South African Railways (CSAR), 22 of the 19 Tonners had survived the hostilities.

This entailed being semi-permanently coupled to a modified side-door suburban passenger carriage which contained a driving cab at the rear, with the regulator, reversing gear and brake controls arranged so that the push-pull unit could be driven from either vehicle.

M1, which was considered to be superior in aspects like design, passenger comfort, economy in running and convenience in working.

Since the imported railmotor was a single vehicle, the carriage was unusable while the engine had to be withdrawn for service or repairs.

[4][5] The initial service on the Pretoria-Rissik and Pretoria-Wonderboom sections attracted so many passengers that it soon became necessary to run a three-coach train.