I'm supposed to be trying to get the etch artwork done, not looking up yet more drawing questions!
But you lot know I can't resist....
It seems strange that Essery's Figure 31 (in Midland Wagons vol 1) is very true to MR drawing number 10 yet he makes no mention of that number in the text (or not that I've found).
Dating from January 1874, it shows two wooden brake blocks acting on both axles on one side of the wagon. I don't believe the MR ever built wagons with a single wooden brake block, but they did inherit some from their acquired constituents, as shown in plates 32 & 33.
There are a few, very subtle, differences in the ironwork between the first and subsequent drawings for these wagons, but if 1874 is early enough for you, Jon, then this casting set will do you fine.
Andy