Years of issue:
4 - Common
The first "new sized" commemorative 50p was issued to commemorate 25 years of the UK in the EEC. Ireland and Denmark also joined Britain in becoming the newest members of the European Community in 1973, bringing the total number of member states to nine. Interestingly, in 1973 Britain's joining of the EEC was the subject of Britain's first-ever commemorative 50p.
You might be interested in:
Wanted – Britain’s most sought-after coins.