50 cent pieces from Australia are large, attractive coins, and some of them are made of silver. As such, they have a collector following and can be valuable, especially when in fully uncirculated condition, like the coin in our picture.
After 1966 the coins went from perfectly round to almost-round 12 sided duodecagons (see secondary picture), and many of the post-1966 coins carry spiffy designs on the reverse instead of the standard kangaroo-shield-emu pattern. These variation makes them attractive to collectors.
Here are the dates for silver coins. All others are made of copper-nickel. Once you determine if your coin is silver or copper-nickel, see the discussion below for values.
1966: 0.341 troy ounces silver
1988: some coins (proofs) are silver, 0.535 ounces
1989: some coins (proofs) are silver, 0.535 ounces
1991: some coins (proofs) are silver, 0.535 ounces
1998: some coins (crown design on reverse) 1.166 ounces
1999: some coins (reeded edge) 0.104 ounces
2000: some coins (Parliament house) 0.586 ounces
For copper-nickel coins after 1974, all are worth face value unless they are in fully uncirculated condition, in which case they might bring $2 to $5 US dollars when a collector wants to add a dazzling specimen to his or her collection. Copper nickel coins between 1969 and 1973 are somewhat more rare, fetching $10 to $20 when fully uncirculated. In average circulated condition, the copper-nickel coins are worth face value: 50 cents in Australia.
The silver coins are worth at least their weight in silver. For instance, if you have a 1988 proof 50 cents with 0.535 troy ounces of silver and if silver is trading at $30 per ounce (look it up on web sites such as kitco.com), then the base value of the coin is 0.535 x 30 = $16. Not too shabby!
A nice-looking example of a silver coin may sell for a few dollars more than the silver value.