Australia has issued large (38 mm diameter) 5 dollar coins since 1988. Coins minted for circulation are made of aluminum-bronze or brass. Coins made especially for collectors and sold at prices well above 5 dollars are made of sterling silver and housed in fancy packaging.
Queen Elizabeth appears on the front of these coins, and various patterns appear on the back.
Coins made of non-precious metal are worth face value: $5 in Australia. A collector will pay as much as $10 US dollars for a superb, fully uncirculated specimen with dazzling eye appeal.
For the silver coins, they are worth their weight in silver. Each coin contains 0.925 troy ounces of silver. Use web sites such as kitco.com to find the current value of silver. It changes every day.