The letters on a car plate designating the car is registered in the country of the Vatican.
An acronym for "Stato della Citta del Vaticano" (Italian), or perhaps "Status Civitatis Vaticanae" (Latin), meaning "State of the City of Vatican."
Because SCV cars tend to be very expensive and comfortable limos for the use of high ranking prelates, some people wonder if SCV really stands for "Si Christus videsse...", i.e. "If Christ (only) saw (it)!"