Built by NBL , it was an improved version of the predecessor Class 4 , with a superheater and Walschaerts valve gear .
In 1913 and 1914 , ten Class 4A locomotives were placed in service by the SAR .
Built by NBL , SAR was an improved version of the predecessor Class 4 , with a superheater and Walschaerts valve gear .
In 1913 and 1914 , ten Class 4A locomotives were placed in service by the SAR .