Apologies if this has been asked before:
R.J. Essery's Midland Wagons Vol 2 p82-83 illustrates a 40T Bogie Bolster wagon, which he describes as “something of a mystery”. They didn't have a MR diagram, but LMS doc implies they had been Midland wagons. Of the four known numbers, one, 335958, had a 1918 Leeds Forge builders plate.
Aren't these essentially the same as the WW1 government contract wagons built by Leeds Forge, 30 of which were subsequently absorbed by the NER; and which have been the subject of a Parkside kit for many years?
