In 1935 the Royal Mint struck a crown to commemorate King George V's silver jubilee. Although the crown had stopped circulating in the United Kingdom in the early 1900s, 714,769 pieces, as well as 2,473 proofs were struck to celebrate the occasion. The reverse design was entirely new, although it featured the familiar motif of St George and the dragon, this time designed by Percy Metcalfe. The edge inscription was * DECUS ET TUTAMEN * ANNO REGNI XXV and it was incuse in the edge, except on some proofs where it was raised.
Besides the standard circulation-style pieces, some crowns were struck to a specimen finish, some were struck in sterling silver rather than the standard .500 silver and some were struck in gold (p81, Davies, British Silver Coins Since 1816, 1982).
Two die varieties of the crown occur - on most coins St George's sword points at a rim denticle but on some it points between rim denticles. Davies reports the the sword between rim denticles can occur on incuse edge proofs and possibly on circulation-style pieces too (p81, Davies, British Silver Coins Since 1816, 1982).
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 - dated 2014, 2015 and 2020 - although their provenance is unknown, it is strongly suspected that they were illegally produced and smuggled out of the Royal Australian Mint.
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). Seemingly a Royal Australian Mint worker once again mistakenly used a 10c obverse die during the production of the 2005 Dancing Man $1 coins. $1 coins with double rims due to off-centre strikes are not uncommon, so most are disregarded as double strikes rather than mules, especially since the Royal Australian Mint is reported to have attempted to prevent the release of the 2000 dollar mules. This would explain why the 2005 mule went undiscovered for so long.
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 $1 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.