Gerard, such a wonderful picture. That bike is what i call the Early Pre-production model, as featured in the March 1969 issue of "CYCLE" magazine. Bob Young was pictured riding one of these Early Pre-production machines. He is wearing a jacket with his name "Bob" embroidered on the front of the jacket.
What i do not know is if the Early Pre-production machine at the Tokyo show is the machine featured in the March 1969 issue of "CYCLE" magazine. Nor do i know if more than one of these machine types were produced. We certainly are inquisitive as to the existence of any of these early p-p machines.
Of interest, these Early Pre-production machine's vins were a 1xxx (4 digit) vin. Chris R can certainly speak to this, but if i recall correctly the vin on the bike Bob Young is pictured is CB750-1110 with engine CB750E-1110.
And, we know the Late Pre-production bike Vic World sold was CB750-2113/CB750E-2113 and Gold Brighton bike was 2110.
I never noticed the thin disc on the Tokyo bike, keen observation, Gerard !