There was the B30 (350 OHV) There was one prototype with Engine No EX 291, one pre production bike with engine EX 309 and then around 200 production bikes with engines WB30 501-700. Ron
Starting with the 1930 model year BSA started the production run on motorcycles at 101.
Thus publicity specials & prototypes were numbered 001 to 100, not that there were many in any case.
Before this it was a right royal mess
The WM23 was the 'Silver Star' for the 1940 Model year but most seem to have been despatched around February / March 1940. Of the 200-odd produced (there were some gaps though) it looks as if 17 went to either of the two Australian agents in Adelaide and Freemantle.