They were successful designs ideally suited to hauling coal trains a relatively short distance.
In 1925, two were rebuilt with the then newly developed number 10 standard boiler and high domed cab by the GWR.
In this form they were visually similar to a smaller version of the GWR 5600 Class introduced in 1924.
The numerous railways of South Wales had one thing in common apart from transporting coal in large quantities; their liking for the 0-6-2T type.
The suitability of the type was because the nature of the work they undertook demanded high adhesive weight, plenty of power with good braking ability, but no need for outright speed, nor large tanks or bunker as the distances from pit to port were short.