32mm(diameter) The original scooter on the street is, yes, the Vespa. The name "Vespa," which means "wasp" in Italian, is derived from its distinctive rear view. Many people are probably familiar with the scooter that Hepburn used to dash across the screen in "Roman Holiday.
There are various clubs around the world that are run by people who love the Vespa. This is a valuable badge made for Vespa Club members in Parma.