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 1951 Halfpenny minted in Melbourne, has no mintmark.
An Australian 1951 Halfpenny minted in Perth has a dot (.) after the (Y) in PENNY (PENNY.).
An Australian 1951 Halfpenny minted in London has a very small PL after the (Y) in PENNY.
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.
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).
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.
Any 1942, 1943 or 1944 Australian Threepence, will have the "S" (San Francisco) or "D" (Denver) mintmark on the reverse of the coin, on the right hand side, just below the fourth digit of the year. Any coins minted in Melbourne will have no mintmark.
The Royal Australian Mint produced no Australian Halfpenny coins from 1956 to 1958 inclusive.
Apart from "AUSTRALIA" and "HALF PENNY", the only letters on the reverse (back) of a 1942 Australian Halfpenny are "KG". They are the initials of the designer of the reverse, George Kruger Gray. The letters "HP" on the obverse (front) (below the back of the King's neck), of all Australian coins from 1938 to 1952 inclusive, are the initials of the designer of the obverse (front), T Humphrey Paget.