In 1930 a group of fifteen new steel open wagons were built for the M.R.W.A. They were numbered PA465-474, 501-505. They were similar in design to the M.R.W.A. P class built in 1927, which were identical to the W.A.G.R. K class. The difference between the two class was that the PA class had sides only 3'-0" high compared to the 4'-0" deep sides of the P and W.A.G.R. K classes. In 1932 for some reason now lost in the mists of time the P class became class PA and the PA class became class P. A further batch of wagons (P460-464) was built in 1932 followed by P455-459 in 1933 and 451-454, 475 in 1934. Finally in 1955 P501-5 were renumbered P446-450. There is a photo of one of these wagons in the Weston Langford collection.

1964	P446-452, 454, 456-463, 465-473, 475 to KB40611-7, 40619, 40621-8, 40630-8, 40640.
1965	P453, 455, 464, 474 to KB 40618, 40620, 40629, 40639

The wagons in this class were written off as follows:

1970	40612, 40626 written off
1972	40616,40617, 40619, 40620, 40629, 40630
1973	40614, 40631, 40632 written off
1975	40622, 40635, 40638 written off
1976	Written off KB40617, 40614, 40619 to JETTY 985-987
1977	40618, 40625 written off
1978	40634 written off
1979	40611, 40613, 40615, 40621, 40623, 40624, 40627, 40628, 40633, 40636, 40637, 40639, 40640 written off