I find it hard to believe as well, looking at the rear number plate there is no transfer with the piled arms and 250cc, I am not sure about what bars were fitted by the factory but in the UK they were straight, they actually made about 900 SS80's in 1962 and they all had the same engine so I do not understand his comment of the about most not having the SS engine. By far the rarer road going C15 would be the Sportsman of which BSA only made about 250 during the whole run of C15's, providng my information is correct.
However it is not impossible but I wonder if he has proof to support his claim?
Richard