PJ&JP wagons belonged to one of South Wales' largest coal companies, the partnership of Partridge, Jones and John Paton. These 20 ton capacity steel bodied wagons were introduced in the 1930s, the railways companies having realised that economies could be achieved if bulk loads were hauled in fewer wagons. The GWR offered a lower rate per ton for coal conveyed in these 20 ton capacity wagons, represening almost twice the load per wagon compared to a conventional 7-plank open, and even offered hire terms. Several of the large coal companies took advantage of these offers.