The locomotives were equipped with Pyle National Electric headlights.
They were the world's first true Mountain type tender locomotives, having been designed and built with a 4-8-2 wheel arrangement with the firebox positioned to the rear of the driving wheels.
Earlier Natal 4-8-2 locomotives were modified from a different original wheel arrangement.

The boilers which were used on these locomotives were, at the time, the largest in South Africa.
Like the altered NGR Class B of 1906 on which it was based, these loco­motives used saturated steam and had plate frames.
They used Walschaerts valve gear with flat "D" gunmetal type valves, which were arranged above the cylinders and controlled by the Hendrie-designed steam reversing gear.
Since they were built without superheaters, the bore of their slide valves were ¹⁄₂ inch (12.7 millimetres) larger than those on the altered Class B of 1906 to compensate for the additional weight of the locomotive.

The boiler, of which the barrel was ¹¹⁄₁₆ inch (17 millimetres) thick, was fitted with four Ramsbottom safety valves, 3 ¹⁄₂ inches (89 millimetres) in diameter.
It was fed by two injectors, arranged on the underside of the footplate at the sides, with the combination valves placed on the back of the firebox.
The Belpaire firebox was constructed with a forward "rake" of the throat and back plates to keep the distance between the boiler's tube plates reasonably short at 18 feet 6 inches (5,639 millimetres).
It had a finger bar firegrate which was operated by hand lever from the cab.
The locomotives were equipped with Pyle National Electric headlights. They were the world's first true Mountain type tender locomotives, having been designed and built with a 4-8-2 wheel arrangement with the firebox positioned to the rear of the driving wheels. Earlier Natal 4-8-2 locomotives were modified from a different original wheel arrangement.
The boilers which were used on these locomotives were, at the time, the largest in South Africa. Like the altered NGR Class B of 1906 on which it was based, these loco­motives used saturated steam and had plate frames. They used Walschaerts valve gear with flat "D" gunmetal type valves, which were arranged above the cylinders and controlled by the Hendrie-designed steam reversing gear. Since they were built without superheaters, the bore of their slide valves were ¹⁄₂ inch (12.7 millimetres) larger than those on the altered Class B of 1906 to compensate for the additional weight of the locomotive.
The boiler, of which the barrel was ¹¹⁄₁₆ inch (17 millimetres) thick, was fitted with four Ramsbottom safety valves, 3 ¹⁄₂ inches (89 millimetres) in diameter. It was fed by two injectors, arranged on the underside of the footplate at the sides, with the combination valves placed on the back of the firebox. The Belpaire firebox was constructed with a forward "rake" of the throat and back plates to keep the distance between the boiler's tube plates reasonably short at 18 feet 6 inches (5,639 millimetres). It had a finger bar firegrate which was operated by hand lever from the cab.
South African Class 3 4-8-2