A friend bought a bike with engine number 357 recently and the frames were 1990 different. I have seen a few variations in the early bikes and it is not only 1990 or 1900 difference. By the way, 357 would have been one of the last 1947 machines as it arrived in Australia on Dec. 31st 1947 after leaving the works on Dec. 3rd. It was considerably cheaper than the one on e-bay but was missing the original guards.