They tended to hang aroud a while in the early days as the cost nearly as much as a Triumph Bonneville. I think yours and mine were probably made on the same day and came over on the same boat.
I did some sanding around the head stock and revealed all 3 colours the eariest being blue.
here are some pics of what I have to work with
The bike as it was in about 1969
race bike by kennethstevenscb72, on Flickrwhat I have to work with now
IMG_0504 by kennethstevenscb72, on Flickr
IMG_0503 by kennethstevenscb72, on Flickr
IMG_0500 by kennethstevenscb72, on FlickrThe race engine in road trim
IMG_0505 by kennethstevenscb72, on FlickrKen