get https://{environment}.{server}.com/v3/card/external-
Get a card using its External ID. For example doing an HTTP get call to [base_url]/card/external-abc will retrieve a card using the user defined External ID of 'abc'.
When tokenizing a credit card it is possible to add an External ID. The External ID can be any alphanumeric string. Credit cards can then be looked up based on the External ID that was set during creation. Simply Prepend the External ID with 'external-'.