Since the other thread got blocked out by the political twists it took, I am posting this new. Prior to the introduction of a unique Irish coinage in 1928 British coins circulated exclusively in Ireland, after 1928 they circulated alongside the Irish coinage. British coins gradually disappeared from circulation after WWII so that afterwards they were rather scarce. It would have been impossible to have removed all British coins from circulation in 1928, there were just too many that had circulated for too long.
Ireland was also weak economically. Stable, but little opportunity for growth. Which meant coinages were low. Because of the traditionalism of Ireland, once the nation got its independence, the people were also quite content to continue using their British coins. Although British coins did disappear around WWII (or the Great Patriotic War, depending on where you're from), Ireland's economy didn't grow much until the "Celtic Tiger" era starting in the late '90s.
I don't remember exactly, but I think Irish Pounds could be exchanged in London at par with Pounds Sterling until 1968.
The currencies fluctuated a very small bit, but essentially they were linked until 1975-1976 or so. For a very brief period the Irish £ was worth more than the British £, but then by the late 1970's the Irish £ started a gradual slide so that it was usually worth about 30-40p less than the British £ This created a problem in Britain as it became possible to salt large amounts of coins with Irish coins which were the same dimensions, similar to what happens in the USA with Canadian coins.
I believe it had less to do with traditionalism and more to do with plain necessity, as you note, Ireland had a fairly undeveloped economy, which couldn't begin to hope to meet all of it's coinage needs. As you also note, Ireland has been rather successful economically of late, which made their transition into the Euro quite smooth.
It was in 1979 that the parity between the English & Irish Pounds were ended.Between 1928 & 1960,the Irish banknotes contained a clause in both Erse & English 'Payable on Demand in London'. For more information you can visit here; www.irishpapermoney.com .As a collector of British Commonwealth banknotes,I do include the modern post-1949 issues (technically not British Commonwealth) for convenience,& it reflects the evolution of the famous Lady Lavery series,which ended in 1976. The most difficult denomination to get as far as the post-1928 pre-decimal coins from Ireland goes,is the Farthing (1/4d.),which is an extremely difficult series to collect,due to the low mintage figures,& that a few dates very seldom turn up (1930,1932,1936, 1937,1959,& 1966).I got an example of the 1936 by chance,& found a 1930 quite recently. Aidan.
