My Shadow was road tested Nov 1952, and left the factory in mid-1953, engine number in the 98xx range. The bike is unrestored, and the Mercury crest is NOT the Vincent Engineers one, it has the Vincent HRD Co Ltd one. The factory had many bikes built in '52 still in inventory well into '53, and given the serial number ranges involved, there can't be very many Series C Vins that would have been built after the company name was changed to Vincent Engineers (Stevenage), which I believe happened sometime in 1953. I think you would have to be into the 99xx range to have the Vincent Engineers style.
I am amazed at how many Series C Vins have the Vincent Engineers Mercury Crests, many with numbers well below the 98xx range. I have raised this point with a very well renowned restorer here in Los Angeles, and it is like he doesn't know there are two different Mercury Crest patterns that have the Vincent scroll. Nearly every Series C that I see that was done by him has the wrong Mercury Crest.