BS ISO 3166‑3:2020 pdf download.Codes for the representation of names of countries and their subdivisions.
4.3 Division of country
A country, dependency or other area of particular geopolitical interest in part I of the ISO 3166 database is divided into two or more new countries, dependencies or other areas of geopolitical interest.
EXAMPLE CZECHOSLOVAKIA (CS) was divided into the CZECH REPUBLIC (CZ) and SLOVAKTA (SK) in 1993.
4.4 Merger of countries
Two or more countries, dependencies or other areas of particular geopolitical interest in part 1 of the ISO 3166 database merge into one new country, dependency or other area of particular geopolitical interest. In this process, the name of at least one of the countries, dependencies or other areas of particular geopolitical interest becomes a formerly used country name.
EXAMPLE 1 YEMEN, DEMOCRATIC (YD) and YEMEN ARAB REPUBLIC (YE) merged into YEMEN, REPUBLIC OF (YE) in 1990 (change of both country names).
EXAMPLE 2 GERMAN DEMOCRATIC REPUBLIC (DD) united with GERMANY, FEDERAL REPUBLIC OF (DE) in 1990 (removal of one country name).
NOTE If the new country name allows no visual association with one of the formerly used code elements, a new code element will be assigned.
4.5 Obsolescence of country name
The area denominated by a country name is absorbed by neighbouring countries and the country name ceases to be used.
EXAMPLE NEUTRAL ZONE (NT); the name was deleted in 1993. The area is now absorbed into IRAQ (IQ) and SAUDI ARABIA (SA).
4.6 Change of status of an alpha-2 country code element
The status ofan alpha-2 country code is changed in a significant way, such as from reserved exceptionally to assigned, or from reserved transitionally to unassigned, or from reserved indeterminately to unassigned.
EXAMPLE ISLE OF MAN (IM): in 2006 the alpha-2 code of Isle of Man changes its status, from exceptionally reserved by UPU in 1974, to assigned.
5 Principles for assigning code elements for formerly used country names
5.1 Structure of code elements for formerly used country names
The code elements for formerly used country names shall have a length of four alphabetical characters (alpha-4 code e1ements. The first two characters are, in all cases, the original alpha-2 code element representing the former country name removed from any edition of ISO 3166 and ISO 3166-1. The coding structure of the second two characters reflects the five categories for inclusion defined in 42 to 46
NOTE The structure of code elements for a particular case of change of country name is defined in 5.6.
5.2 Change of country name (see 4.2)
The original alpha‑2 code element is followed by the alpha‑2 code element for the new country name.
EXAMPLE BURMA (BU) name change to MYANMAR (MM).
Code element for formerly used country name for BURMA: BUMM.BS ISO 3166‑3 pdf download.