Czech license plate: Test (documented since 2001)

Format, years and the law

Format: F99 99, for example F42 51 (9 any digit)
The format above follows the issuing rules: a registration that fits it is one this series could have issued.
Years issued: Documented since 2001; the format is likely older than the first year documented. Still issued.
Vehicle class: Dealer: trade/garage plates bound to a business, not a vehicle. Issued for car, van, truck, bus, motorcycle, trailer, and machine.
Colours: Characters #009933 Background #FFFFFF
Size: 520 × 110 mm · every country's size
About this plate: THE TEST PLATE, F plus four digits, green on white, issued only with the Ministry of Transport's prior consent and only for vehicles whose technical fitness has not yet been approved or which are carrying unapproved parts. The reservation of the letter F is why vyhláška 243/2001 Sb. kept F out of the ordinary letter alphabet altogether; when the 2014 regulation re-admitted F to that alphabet it kept the reservation here too, so F is now positionally ambiguous and a parse API must use the five-character length to disambiguate.

The series id is cz-test. The API returns its format, validation, colours and designs with the rest of Czechia's series:

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