 Collectively they became the blueprint for the 200 strong 5600 class.The design of the 5600 class followed the Rhymney designs quite closely but adopted GWR practice as far as possible, by utilising many standardized parts.Included in Collett’s innovations was a standard number 2 boiler which was suitable for the 5600 (and the M and R class Rhymney locomotives), complete with the traditional copper GWR safety valve casing and copper-capped chimney.