Well you'll have to be surprised Rik. These have never had bearings or a barrel on them. I bought them from a top engine builder [fastest bike at Red Marley Hill climb last year] He said there wasn't a mark on them , and there isn't
Nothing has ever been threaded into the cases. I took them round to another bike builder who has a '46 overhead valve motor in a road race prewar frame and he said the same. I have photos but have no idea how to post. I tried sending you the photos but they got bounced back. Not sure if I had the correct email address.
I have an "Illustrated Spare Parts List" for engine/frame W 26001-43000 contract 294/C/7353 which lists "Crankcase with Timing Cover, Magneto Chain Cover, Bushes,Studs, Bolts and Nuts complete" as part number 3677.
There was no Field Stand no Racks and no Sump Plate in the list so it's possible that prior to fitting the sump plate spare cases were included.
I paid a bit less than you did.