No. Australian Coins, with the exception of the 50 cent coin which is 12 sided or dodecagonal, come in the regulation shape of "round".
All coins have length, width and depth, and are thus 3D objects. The Australian 50 cent coin has twelve sides, and so is dodecagonal in shape.
The Australian 1966 50 cent coin was the first and last round Australian 50 cent coin produced by the Royal Australian Mint. With the wisdom of hindsight, this coin was a bit of a blunder on the part of the Royal Australian Mint. It was only very slightly larger in size to the Australian 20 cent coin and it had an 80% silver content at a time when the price of silver was increasing rapidly. It took only three of these coins to get one ounce of silver.
on the Australian 20 cent coin it the platypus
Yes, the 10 cent coin is smaller. The Australian 10 cent coin is 23.60 mm in diameter. The Australian 20 cent coin is 28.52 mm in diameter.
Other than the initial Australian 1966 50 cent coin which was round, all subsequent Australian 50 cent coins from 1969 have been dodecagonal or 12 sided. Because they are of a similar size to the 20 cent coin, they were made 12 sided so that vision impaired people could feel the difference.
The Australian 5 cent coin has an echidna on it?
Such a coin does not exist. The Australian 1 cent coin was first issued in 1966. The Australian One Penny coin was issued from 1911 to 1964 inclusive.
Australian two-dollar coin was created in 1988.
Australian five-cent coin was created in 1966.
Australian twenty-cent coin was created in 1966.
Australian one-dollar coin was created in 1984.
The first Australian Dollar coin was issued in 1984.