The three G class locomotives were introduced by NZR in response to increased tonnages, especially on the mountainous, demanding North Island Main Trunk Railway.

However, various faults led to their swift withdrawal from service and NZR still needed a large and powerful type of locomotive.

[1] Constructed at Hutt Workshops, the class utilised plate frames, partial mechanical lubrication, Franklin butterfly Firehole doors, and roller bearings on all but the trailing bogie.

K 919 was given an ACFI feedwater heater system as a trial, a feature that was continued on the subsequent KA and KB classes.

After the Second World War, a coal shortage occurred and NZR converted a large number of locomotives to oil burning.

It was then transported to the main MOTAT site and placed at the rail pavilion in the company of AB 832, F 180 Meg Merrilies, J 1236, WW 491, and diesel-electric locomotive DA 1400.

It appears much as it was when withdrawn, with the recessed K-style headlight, but with a KA style funnel and a cross-compound pump with twin air reservoirs mounted under the front compressor shields.

This was put on hold prior to the move to Plimmerton, at which point the boiler was lowered back onto the overhauled frames for storage.