The problem is that apparently nobody ever did some serious research on the WD Ariel models. Definitely not in the same way as I have researched the WD Royal Enfields, and others have done the WD BSA and WD Norton. So... Census number styles before 1942 are a bit "chaotic", but period photographs from 1942 onwards show very distinctive styles for the census numbers on the different makes. I have made DXF drawings of the Royal Enfield census number style, low tack stencils are available from Axholme. The typical "styles" for the other makes can be seen below:



As can be seen above and below, Ariel had a very distinctive "stencil" style. The fact that this was unique to Ariel, and the fact that every factory had its own unique style, proves that the census numbers were applied at the factory (at least from 1942 onwards). The paper that I added to a previous post proves that the census number can be calculated for each contract (again: at least from 1942 onwards).

email (option): wd.register@gmail.com