The Australian Halfpenny was issued with two basic reverse designs.
The earlier design
1911 to 1939 - reverse legend reads "COMMONWEALTH OF Australia" around the circumference and "ONE HALF PENNY" in the centre. The year is at the bottom.
If the coin has a mintmark at all, it will be an "H" or an "I" below the middle "N" in PENNY. "H" indicates the Heaton Mint in Birmingham, "I" indicates the Calcutta Mint in India.
All Australian Halfpennies minted from 1911 to 1918, if they have no mintmark, were minted at the Royal Mint London.
All 1912 and 1915, and some 1914 Halfpennies were minted at the Heaton Mint, Birmingham.
All 1916 to 1918 Halfpennies were minted at the Calcutta Mint, India.
All other Halfpennies were minted at either the Melbourne or Sydney Mints and have no mintmark.
The later design
1939 to 1964 - reverse legend reads "AUSTRALIA" around the circumference at the top and "HALF PENNY" around the circumference at the bottom. These coins feature the right facing hopping kangaroo. The year is below the kangaroo and slightly left of centre.
Halfpennies with no mintmark were minted at the Melbourne Mint.
Halfpennies with a dot "." after the "Y" in PENNY (PENNY.) were minted at the Perth Mint.
Halfpennies with a dot "." after the "A" in AUSTRALIA (AUSTRALIA.) were minted at the Perth Mint (1952 and 1953 only).
Halfpennies with a very small "PL" after the "Y" in PENNY (PENNY PL) were minted at the Royal Mint London (1951 only).
Halfpennies with a very small "I" after the "Y" in PENNY (PENNY I) were minted at the Bombay Mint, India (1942 and 1943 only).
An Australian 1942 Halfpenny minted in Melbourne, has no mintmark. An Australian 1942 Halfpenny minted in Perth has a dot (.) after the (Y) in PENNY (PENNY.). An Australian 1942 Halfpenny minted in Bombay has an (I) below the King's head.
An Australian Penny or Halfpenny with a "Y." (PENNY.) mintmark indicates that the coin was minted at the Perth Mint. An Australian Penny or Halfpenny with a "I" mintmark indicates that the coin was minted at either the Calcutta or Bombay Mints in India.
The Australian 1943 Penny was minted variously at the Melbourne Mint (no mintmark), Perth Mint (mintmark is a dot after the Y in PENNY "Y.") and Bombay Mint (mintmark is an "I" under King George's bust).
KG is not a mintmark, it is the initials of the designer of the (kangaroo) reverse of the Australian 1938 to 1964 Penny and Halfpenny coins, George Kruger Gray. 1940 and 1941 Pennies minted at the Perth mint have a dot between the K and the G (K.G) as the mintmark.
There were was no Australian 1956 Halfpenny minted.
The last Australian Halfpenny was minted in 1964.
The last Australian Halfpenny was minted in 1964.
The last Australian Halfpenny was issued in 1964.
The Royal Australian Mint produced no Australian Halfpenny coins from 1956 to 1958 inclusive.
An Australian 1951 bronze Halfpenny (George VI)(minted in London - mintmark = PL), uncirculated and in absolute mint condition could fetch up to $22 AUD. If it has been circulated but still in good condition, it might fetch anything from $0.50 to $6 AUD. There were 6.96 million minted. An Australian 1951 bronze Halfpenny (George VI)(minted in Melbourne - no mintmark), uncirculated and in absolute mint condition could fetch up to $65 AUD. If it has been circulated but still in good condition, it might fetch anything from $1 to $15 AUD. An Australian 1951 bronze Halfpenny (George VI)(minted in Perth - mintmark = Y.), uncirculated and in absolute mint condition could fetch up to $52 AUD. If it has been circulated but still in good condition, it might fetch anything from $0.50 to $7 AUD. There were a combined total of 29.422 million minted at both Melbourne and Perth. An Australian 1951 bronze Halfpenny (George VI)(Proof)(minted in London - mintmark = PL), uncirculated and in absolute mint condition could fetch up to $25,000 AUD. An Australian 1951 bronze Halfpenny (George VI)(Proof)(minted in Melbourne - no mintmark), uncirculated and in absolute mint condition could fetch up to $30,000 AUD. An Australian 1951 bronze Halfpenny (George VI)(Proof)(minted in Perth - mintmark = Y.), uncirculated and in absolute mint condition could fetch up to $30,000 AUD. A reputable coin dealer will be able to give a more accurate valuation.
The Royal Australian Mint produced no Australian Halfpenny coins from 1956 to 1958 inclusive.
An Australian 1916 bronze Halfpenny (George V)(minted in Calcutta - mintmark = I - below bottom scroll), uncirculated and in absolute mint condition could fetch up to $500 AUD. If it has been circulated but still in good condition, it might fetch anything from $0.75 to $85 AUD. There were 3.6 million minted. An Australian 1916 bronze Halfpenny (George V)(Proof)(minted in Calcutta - mintmark = I - below bottom scroll), uncirculated and in absolute mint condition could fetch up to $35,000 AUD. A reputable coin dealer will be able to give a more accurate valuation.