No, of course it's not! I own one!
Check your Vincent history. From memory about 40 "Comet Specials" left the HRD-Vincent factory around 1935-1937. They were also designated TTC. They were basically road-going Series A Comets but fitted with slightly de-tuned TT Replica racing engines with bronze heads, TT Carbs, TT Forks, TT Brakes, etc. Customers could tweak the spec as they wished, but when each left the factory it was a factory standard "Comet Special".
http://thevincent.com/vinprod.html
Peter B
Bristol, UK.
TTC 20 - Comet Special.