Complex sentence: When the Irish Free State came into existance in 1922 three types of banknote were in circulation, these were issued by the Bank of England, British Treasury and the several Irish banks then in existance who were chartered to issue notes.
Split into simpler sentences: When the Irish Free State came into existance in 1922 three categories of banknote were in circulation. These consisted of notes issued by the Bank of England, the British Treasury and several Irish banks then in existance who were chartered to issue notes.