The Australian 2000 $1/10c mule is well known, having been discovered in the early 2000s. A number of other similar errors have since come to light - 2014, 2015 and 2020 - although their provenance is unknown, but almost certainly illegally smuggled out of the Royal Australian Mint. $1 coins with double rims due to off-centre strikes are not uncommon, so most double rims are disregarded as double strikes due to the very low probability of a mule occurring in yet another year.
A 2005 Dancing Man $1/10c mule was reported in the April 2025 Independent Coin News, having been discovered by collector Brendan Alves in February 2025 (Andrews, https://www.independentcoinnews.com/April_2025.pdf). Currently only a single well-circulated example from circulation is known: no doubt there are others waiting to be found, but it remains to be seen if the error is limited to circulating coins or to just the Dancing Man coins.
In 1964 the Heaton Mint in Birmingham struck Hong Kong's 10c pieces. All pieces were struck with a security edge rather than a milled edge, except for a single known piece struck with a milled edge and the letters HK repeated around the milling.
The nature of the piece is unclear but was no doubt an experimental piece, although it's not clear to what end - the security edge would no doubt be more difficult for forgers to replicate, but perhaps the costs associated with the security edge were higher than desired.
The single known example was offered for sale by Smalls Auctions' March 2025 sale as lot 217 but was unsold.
As it has for many years, in 2024 the Royal Australian Mint produced a non-circulating one dollar coin that was available to counter-stamp and purchase at various locations throughout Australia, including at the Royal Australian Mint itself. In 2024 the one dollar coin's design commemorated Australia in Space. The coins were struck at the Royal Australian Mint and counter-stamped on location.
Most mules are the result of using an incorrect obverse or reverse die, though very occasionally an incorrect collar die is used. A modern example of an incorrect collar die mule is the 2025 George Orwell 1984 £2 from the Royal Mint's Strike Your Own press.
On 20th January 2025 the Royal Mint changed the Strike Your Own coin design from the definitive flora design to the George Orwell 1984 design. It would appear that the Royal Mint staff did not update the blanks however, and a small number of planchets with the edge inscription IN SERVITO OMNIUM were struck with the George Orwell 1984 design. The expected edge inscription for this design was THERE WAS TRUTH AND THERE WAS UNTRUTH.
Australia's 1939 halfpennies were struck with with two major designs - Blakemore's token design and Kruger Gray's kangaroo design. Most other denominations had their reverses updated in 1938 but the halfpenny's new reverse came later, and even then in 1939, 4,382,000 halfpennies were struck with the old design and just 504,000 were struck with the new design, making the 1939 kangaroo halfpenny a scarce coin.
Within the strikings of the 1939 kangaroo halfpennies there are a number of varieties: the dies for the new design were produced at the Royal Mint, London but they did not correctly fit the Melbourne Mint's die presses, which necessitated some changes (p214, Briggs, Australia Copper/Bronze/Brass Halfpenny Die Types, 2016).
1939 kangaroo halfpenny reverse dies
Reverse Die
Notes
Fur on arm Deep rib-cage in front of knee Both serifs on base of Y of PENNY
Very rare
No fur on arm Shallow rib-cage in front of knee Right serif on base of Y of PENNY missing
Most common
No fur on arm Deep rib-cage in front of knee Right serif on base of Y of PENNY missing
Use for proofs
The original dies were apparently used to strike a small number of coins which were subsequently released into circulation: they are rare, but as it is a comparatively recent discovery, no doubt more will come to light. The updated design is largely the same but the details of the fur on the kangaroo's arm and the kangaroo's rib-cage are gone. Curiously, the right serif on the foot of the Y in PENNY has been removed - possibly in error unlike the other changes. The design used for the 1939 halfpenny proofs appears to represent an intermediate design as it still has the deep rib-cage of the original design - possibly is was tested but found to be unsatisfactory for long term use and so was relegated to the striking of proofs. Interestingly a proof is known with the original design but there is speculation that it was in fact struck at the Royal Mint, London (https://benchmarkcoincatalogue.com/coin/412?pg=79).