| Custom codes for both historic and future use |
|
| ZZN |
North America NOS |
| ZZC |
Central American NOS |
| ZZS |
South America NOS |
| ZZP |
Pacific NOS |
| ZZE |
Europe NOS |
| ZZF |
Africa NOS |
| ZZA |
Asia NOS |
| ZZX |
Non-US NOS |
| ZZU |
Unknown |
| Custom codes for historic use only |
|
| XNI |
North American Islands |
| XCB |
Other Caribbean Islands |
| XEN |
England, Channel Islands, Isle of Man |
| XSC |
Scandinavia |
| XGR |
Germanic Countries |
| XSL |
Slavic Countries |
| XCZ |
Czechoslovakia (former) |
| XYG |
Yugoslavia (former) |
| XUM |
Ukraine and Moldova |
| XNF |
North Africa |
| XSD |
Sudanese Countries |
| XWF |
West Africa |
| XSF |
South Africa |
| XEF |
East Africa |
| XIF |
African Islands |
| XET |
Ethiopia and Eritrea |
| XAP |
Arabian Peninsula |
| XIS |
Israel and Palestine |
| XCR |
Caucasian Republics of former USSR |
| XOR |
Other Asian Republics of former USSR |
| XSE |
Southeast Asia |
| XMS |
Malaysia, Singapore, Brunei |
| XCH |
China, NOS |
| XML |
Melanesian Islands |
| XMC |
Micronesian Islands |
| XPL |
Polynesian Islands |
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