What's the history behind 1955 and 1956 being the "Line in the Salt" so to speak between Vintage and Modern Motorcycle classes? I have tried to search the archives but found nothing. Is it because 1956 was when the NSU factory assault on the streamliner records was made? Anybody out there have any facts on the subject? If not then any other theories? Just became curious as I was strolling through the Sammy Miller Motorcycle Museum in New Milton, Hampshire, UK looking at lots of old bikes last week.