I have just come across a 18" WM3 rear wheel, crinkle hub, spline fitting, complete with brake hub & sprocket in good condition, axle & adjusters. I am not sure what it came off but it is definitley military as it still has olive paint on it, I would imagine maybe a BSA B40 S/A model or I suppose it could have been used on another model for sidecar work, galvanised spokes.
This item is for sale, if anyone would like it drop me a line.
18" rims were used on some M20 sidecar contracts...however, the 'crinkle hub' was a post war development so if the (gloss) green is original the GB40 is the most likely candidate....Ian