Latvian license plate: Transit (documented since 2010)

Format, years and the law

Format: LL9999, for example HS3358 (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 2010; the format is likely older than the first year documented. Still issued.
Vehicle class: Temporary: short-validity plates (transit, awaiting registration). Issued for car, van, truck, bus, motorcycle, and trailer.
Colours: Characters #000000 Background #FFFFFF
Size: 520 × 110 mm · every country's size

Transit 240×130 mm

temporary · 240 × 130 mm
About this plate: THE TRANSIT PLATE, which is also Latvia's EXPORT plate. Note precisely what the red is: a red FIELD placed on the plate, not a red ground and not red characters, the regulation uses a different formula for each of its three red plates and this file keeps them apart. The red field's dimensions and position are stated only as "noteikta izmēra" (of specified size) without giving the size, which is a real gap in the instrument itself and is recorded as such rather than filled from a photograph.
How long it is valid: rule: CSDD: 'Tranzīta numura zīmju derīguma termiņš ir 30 dienas.', 30 days.. purpose: MK 1080 p.

7. pielikums 4.1.1-4.1.2; punkts 13.1 https://likumi.lv/ta/id/222145-transportlidzeklu-registracijas-noteikumi
CSDD: the 30-day validity https://www.csdd.lv/transportlidzekla-numura-zimes/tranzita-numura-zimju-sanemsana

The series id is lv-transit. The API returns its format, validation, colours and designs with the rest of Latvia's series:

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