Revenue stamps of the United Kingdom
When Ireland was partitioned into Northern Ireland and Southern Ireland in 1921, separate revenue stamps were issued for both entities. Southern Ireland stamps saw little use since that political entity was quickly superseded by the Provisional Government of Ireland and later the Irish Free State (both of which applied overprints on various British and Irish revenue stamps). However, Northern Ireland continued to use separate revenue stamps until the 1980s. Northern Irish revenues include Civil Service, Dog Licence, Excise and National Insurance stamps, among many others.
Counties of Northern Ireland
The English administration in Ireland in the years following the Anglo-Norman invasion of Ireland created counties as the major subdivisions of an Irish province. This process lasted a period from the 13th to 17th centuries, however the number and shape of the counties that would form the future Northern Ireland would not be defined until the Flight of the Earls allowed the shiring of Ulster from 1604.