There are two sorts of Longstroke covers. Early ones have a "Flat Bottom." Prone to leakage, they were slightly modified to the later type (1949/50) with an extra retaining bolt on the flat lower edge, so have a "Dimple" These covers do not fit the Bert Hopwood later crankcase, despite the descriptions on your favourite auction site. The dynamo housing top edge is more horizontal on these early cases, which have their own gaskets as well.
Post 1950 shortstroke crankcase both Plunger and S/A engines covers are interchangeable castings Some have "Carrots" below the piled arms logo.
For the more exotic variants, the covers are slightly different depending on the take off for the Tacho drive, either oilpump or maggie driven. These could be used on the basic engines with the drive blanked off.
At one time outer covers were one of the most common items at autojumbles, and you could take your pick. Bit rarer now, but still a bit overpriced by some folks for such a simple casting. Think about something else and one will appear........
Works for me
Swarfy.
