Lithuanian license plate: Trailer (documented since 2004)

Format, years and the law

Format: LL 999, for example JJ 136 (L is any letter, 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 2004; the format is likely older than the first year documented. Still issued.
Vehicle class: Trailer: trailers and semi-trailers where separately serialized. Issued for trailer and semitrailer.
Colours: Characters #000000 Background #FFFFFF
Size: 520 × 110 mm · every country's size

Trailer 300×150 mm

trailer · 300 × 150 mm

PRIMARY (authority): trailers and semi-trailers carry 'two letters and three numbers', on formats 1 and 2 https://www.regitra.lt/en/services/state-number-plates/types-of-vehicle-registration-number-license-plates/of-general...

The series id is lt-trailer. The API returns its format, validation, colours and designs with the rest of Lithuania's series:

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