It could be a Peel "Mountain Mile" fairing as used frequently on British Racing machines of the late '50's? / early '70's.
But then it could also be intended for road use as they also made fairings for Honda machines of the sixties, among others - an aperture for a headlamp would be a dead giveaway.
The number on the plate may identify it if you can find someone in possesion of the factory records.
Peel also built a microcar with a 50cc engine called the P50 in the early sixties, to be followed a couple of years later by the "Trident" with a larger engine of 98cc and revised styling.
Try "googling" "Peel mountain mile" and "Peel microcar" .
Unpainted and never mounted with the plate intact? Someone will want that!
Let us know what you find out.
A.
