That's an easy one. It is the Tinkler. This was an early attempt at unit construction with a fully enclosed power unit and gear box.
The inventor took it to the IoM but I believe it only appeared in practice and didn't race.
I think the E on the racing plate stood for Experimental but I'm not sure.
I've seen drawings of the power unit in the magazines of the day but this is the first time I have ever seen it in a bike and on the road. Thanks Dave for finding the picture.
Cheers,
