2008 20 Cent Varieties
In the early 2010s it was noticed that a small number of 2008 Australian 20c pieces had a small gap between the wave and the playtpus' head, similar to the wave gap used as a mintmark on 1966 20c pieces. While it is a part of the design that is subject to die fill, it was realised that it was likely a genuine variety as the 2008 Wedding Set coins all exhibit the same wave gap. With a mintage of just 3,278 sets, the wave gap was unlikely to be due to die fill, especially as Wedding Set coins were specially struck. It seems likely that the Royal Australian Mint accidentally deployed a Wedding Set reverse die for the production of some circulating 20c pieces, though it is unclear why such a design change was made for the Wedding Set coins. The wave gap reverse design has not been noted on any other contemporary 20c pieces so it did not supercede the then in-use reverse design.
While the wave gap variety makes up a very small percentage of the total mintage, with 132,900,000 2008 20c pieces struck, there were approximately 1,000,000 wave gap coins struck. While a study has not been carried out, the high number of wave gap coins struck would suggest that more than one Wedding Set reverse die was used too.