this is a short list of the copper coins. 1/2 penny- 1923, 1916 mule(huge money) plus high grade king george the fifth coins...
penny 1925, 1930 ,1946 are key dates, the 30 being the big one, plus most high grade(near uncirculated or better) king george the fifth which is 1911 to 36..
terry if your mum has a real holey dollar and dump, its big time and would cause a stir in the australian coin world. the big auction houses would climb over each other to get it into their auction.