I think that the Club machine registrar and the Club researcher could tell you with some knowledge. In lieu of sound knowledge, I would answer that it depends on the year and the records. Prior to November 1948 most of the twin racers and specials had a “1A” or “1B” as a design divider in the engine number. This covers a period of time before the Black Shadow and the Black Lightning were official models. Then there was probably a period where Mr. Vincent called certain bikes “Black Lightnings” but there was no official distinction in the factory drawings. In November of 1948 Phil Irving issued a memo instituting the designation of “1C” as the design number or design divider for the Black Lightning. I am not certain that the there was ever a model officially designated as a White Lightning, but Dennis Minett who ran the Special Engine department at the Factory does list a “1A” machine as a “White Lightning” in his notebook. So, if your bike has a 1A design number and is listed among the bikes that were built in the Special Engine Department, I should think you could call it a White Lightning or a White Shadow with some justification. If the build sheet shows many special Shadow parts, but it did not go to the Special Engine Department, I think you could be justified in calling it a White Shadow. If the bike has been customized with Shadow or Lightning parts, call it anything you wish – just give a nod to those that have the real thing and enjoy the ride.
David