Four is the correct answer Erik, congratulations.
You have won an Australian Silver 1966 round fifty cent coin in UNCIRCULATED condition.
1966 was the only round silver 50 cent coin issued in Australia they then issued a 12 sided 50 cent coin.
The original, round, 50c coin was made of 80% silver and 20% copper; but as the value of a free-floating silver price became higher, the coin's bullion value became more valuable than its face value; so that version was withdrawn from circulation and replaced with the dodecagonal cupro-nickel version.
If you already have one, let me know and I will find something else for you.