A work made by an officer or employee of the Government or State of Ireland in the course of his or her duties, created before 1st January 1974; or
A work made by an officer or employee of either House of the Oireachtas in the course of his or her duties, created before 1st January 1974; or
A sound recording, film, live broadcast or live cable programme of the proceedings of either House of the Oireachtas created before 1st January 1974; or
A bill or enactment of the Government of Ireland made available to the public before 1st January 1974.
as per clause "Irish stamps issued before 1984 are official works and those over 50 years old are in the public domain." in Commons:Stamps/Public domain#Irland