The sixty-four O class hoppers, which belonged to the M.R.W.A. were all built for them by the W.A.G.R. The first batch were 901-916 in 1933/4 followed by 917-931 in 1934/5, 932-941 in 1937, 942-951 in 1938 and 952-964 in 1939. When the M.R.W.A. was taken over in 1964 there was some confusion as to how these wagons should be classified. Most of them were reclassified LA before the decision was taken to put them all into class L.

1964	O 902-4, 907, 909, 910-3, 919, 928, 929, 932-4, 937, 9388, 942-4, 946-8, 951-3, 955, 960, 961, 964 to LA 40542, 40547, 40549, 40550-3, 40559, 40568, 40569, 40572-4, 40577, 40578, 40582-4, 40586-8, 40591-3, 40595, 40600, 40601, 40604
1965	O 901, 922, 958 to L40541, 40562, 40598 O 905, 906, 908, 914-8, 920, 921, 923-7, 930, 931, 935, 936, 939, 940, 941, 945, 949, 950, 954, 956, 957, 959, 962-3 to LA 40545, 40546, 40548, 40554-8, 40560, 40561, 40563-7, 40570, 40571, 40575, 40576, 40579, 40580, 40581, 40585, 40589, 40590, 40594, 40596, 40597, 40599, 40602, 40603 LA40559, 40570, 40574 written off LA40452-40552, 40556-8, 40560, 40561, 40563, 40566-9, 40571-3, 40575-40597, 40599, 40601-4 to L
1966	LA 40533 written off LA 40600 to L
1970	40556, 40558, 40585 written off
1972	40541-40552. 40554, 40555, 40557, 40560-9, 40571-3, 40575-40584, 40586-40604 written off
The MRWA outline diagram is shown below.