, i think mostly down to number plate dealing ,
That might be getting closer to the mark.
Didn't ClassicBike or someone show a frame with 20 or 30 numbers stamped into it !
I'll post photos of the lighter tank mounting brackets later.
Those lighter/sculpted tank brackets may just be stock ES2 style postwar brackets.
What else used them may need some researching.
Inters used something different ? Heavier/thicker, or detachable, etc ?
And the one at the right rear was higher, to clear the carb. ?
Inter girder forks were narrower than what the 16h etc used, what is the width between fork blades where the front hub sits ?