ISIL (International Standard Identifier for Libraries and Related Organizations)
The ISIL is used to identify libraries and related organisations (ISO 15511). The identifier is variable length up to 15 characters that may use digits, letters (case insensitive) hyphens, colons and slashes. The non-alphanumeric characters are part of the identifier and are not just for readability.
The identifier consists of two parts separated by a hyphen. The first part is either a two-letter ISO 3166 country code or a (not two-letter) non-national prefix that identifies the agency that issued the ISIL. The second part is the is the identifier issued by that agency.
Only the first part can be validated since it is registered globally. There may be some validation possible with the second parts (some agencies provide web services for validation) but there is no common format to these services.