OK, what I did was, I went to official sites of the places and used their calculators to find the year at which the currency had ten times the purchasing power compared to now. So if you had a unit of currency at that year, you would need ten units to get the same amount of stuff today. The figuring took into account any changes to the currency in use, by the way.
Australia - 1974
Canada - 1964
Ireland - 1974
New Zealand - 1976
USA - 1966
UK - 1974
As for Atlantis, they have perfected money to the point that a clam today is the same value in clams as a clam at any point in time.