Used to identify the international affiliate country code. The values to be used are
those of ISO 3166 -1:1977. The ISO 3166 table has three separate forms of the country
code: HL7 specifies that the 3-character (alphabetic) form be used for the country
code.
Refer to HL7 Table 0399 – Country code in section 2.15.9.17 for the 3-character codes
as defined by ISO 3166 table.