custodian_country_code

For the avoidance of doubt, this is the custodian’s country of residence.

Custodian is well defined, for example in the Eurosystem Monetary Framework Regulation:

‘custodian’ means an entity which undertakes the safekeeping and administration of securities and other financial assets on behalf of others;

Custodians safeguard securities, hold them physically or electronically, and manage related tasks for the security owner. They can be a financial institution, or for example a US Resident Central Securities Depositories (CSD):

An organization that manages or administers the custody or safekeeping of stock certificates, debt securities, or other assets for institutional and private investors. Their residency is in the United States, including a U.S.-resident affiliate of a foreign custodian.