I found a coin from Australia recently and want to know the worth of it on its native soil?

Question

the coin has a bigger size as does a fifty cent piece but much heavier. on the front it has Queen Elizabeth the ll ,the back has a platypus swimming and the numbers 20 over the top of it

Answer 1

It's worth 20 cents.  depends on where you are from take it into an exchange place and find out from them

Answer 2

I'm Australian - yes, it's worth 20cents, so not much.