Vatican City license plate: Prova (1930 to today)

Format, years and the law

Format: SCV 999, for example SCV 315 (9 any digit)
The format above is broad: a registration that fits it has the right shape, which does not show that this series issued it.
Years issued: 1930 to today. Still issued.
Vehicle class: Dealer: trade/garage plates bound to a business, not a vehicle. Issued for car, van, truck, and motorcycle.
Colours: Characters #000000 Background #FFFFFF
Size: 200 × 275 mm · every country's size
About this plate: TEST / TRADE PLATES, for new vehicles moved through Italy or exported. Reported to follow the Italian "prova" pattern, which fits the wider picture of Vatican plates being made to Italian templates by the Italian state printer. Everything here is secondary and the period is not established at all.
Format notes: The word PROVA is a LEGEND printed in red on the upper line, not part of the serial, so it does not appear in the pattern; the serial proper is the sigla plus a progressive number.

it.wikipedia.org https://it.wikipedia.org/wiki/Targhe_d%27immatricolazione_della_Citt%C3%A0_del_Vaticano

The series id is va-prova. The API returns its format, validation, colours and designs with the rest of Vatican City's series:

curl -s https://vehiclesdb.com/api/v1/plates/va \
  -H "Authorization: Bearer $VEHICLESDB_API_KEY" \
  | jq '.series[] | select(.id == "va-prova")'