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 Southern Ireland stamps saw little use since that political entity was quickly superseded by the Provisional Government of Ireland and later the Irish Free State (both of which applied overprints on various British and Irish revenue stamps).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.
Flag of Ireland
In 1921, Ireland was partitioned, with the unionist-dominated north-east becoming Northern Ireland, while later, in 1922, the remainder of Ireland left the United Kingdom of Great Britain and Ireland to form the Irish Free State. Northern Ireland continued to use the UK's Union Flag and created its Ulster Banner derivation of the flag of Ulster with a crown on top of a six-pointed star. Furthermore, for many years the tricolour was effectively banned in Northern Ireland under the Flags and Emblems (Display) Act (Northern Ireland) 1954 which empowered the police to remove any flag that could cause a breach of the peace but specified, rather controversially, that a Union Flag could never have such an effect. In 1964, the enforcement of this law by the Royal Ulster Constabulary at the behest of Ian Paisley, involving the removal of a single tricolour from the offices of Sinn Féin in Belfast, led to two days of rioting. The tricolour was immediately replaced, highlighting the difficulty of enforcing the law.