International vehicle registration code system is used for vehicles belonging to the diplomats of foreign countries with license plate from the host country. That system is host country-specific and varies largely from country to country. For example TR on a diplomatic car in the USA indicates Italian, not Turkish. Such markings in Norway are indicated with numbers only, again different from international standards (e.g. 90 means Slovakian. International vehicle registration code The country in which a motor vehicle's vehicle registration plate was issued may be indicated by an international licence plate country code, formerly known as an International Registration Letter or International Circulation Mark.
Diplomatic vehicle registration plate diplomatic license plates vary from country to country. They often feature the letters "CD" (for ""Corps Diplomatique""), "D" (for "Diplomat") or prefix of international organisations with diplomatic privileges, such as "EU" (for "EUROPEAN UNION") and "OSCE" (for "Organization For Security And Co-operation In Europe"). Diplomatic vehicle registration plate Most countries issue diplomatic license plates to accredited diplomats. Per the Vienna Convention on Consular Relations, these are special vehicle registration plates which typically have distinctive features to allow diplomatic vehicles to be distinguished from other vehicles by police and other bodies, allowing them to give diplomatic vehicles special treatment and warning