love the video Jonesy! What a great mower you've got there. I reckon it would probably be your best score yet. Regarding the float bowl image, are you refering to notch in the lip of the bowl? I've got two or three that match that exactly and just assumed it was designed as an overflow groove. My circlip carby doesn't have a notch in the bowl, but one ore two later style carbys I have do.
Can't help on the coil question, but maybe the coil size changed a little over the life of of the model 2 - just a guess.
Two things I noticed about your roto - the back wheel/s is on the wrong way around and the top port cover should have a brass dome nut - check the bottom port cover as it might have been put on the bottom one instead. Other than that, you've got a real museum quality piece there!
