Greg Shchepanek These are our standard 20 cent pieces, there are always limited editions of some of these coins which are made, usually to commemorate a special event and that's probably the rarer version you referring to. A platypus is a magical little cute animal, I have seen them in the wild and they are adorable. Probably one the craziest looking animals found, they thought a taxidermist was having a laugh when a specimen was first bought to Europe. Let me know if you want more info on these coins. I visited the mint where these coins are made many years ago