Spotted today in London, England. What is this clear plastic shelf below the car's license plate?
It's for mounting the taxi license plate.
https://www.mogo.co.uk/products/rear-bracket-adjustable-for-square-tx-licence-plate
Solved!
Oh that's just where they put the cheese.
Now I feel stupid for even thinking otherwise.
Let us help you identify that mysterious object you’ve found.
Currently in CHALLENGE mode: If you've got something obscure knocking about, post a picture, and let's see how we do. Please prefix such posts with "CHALLENGE:" so we know we've got a fighting chance.