2004 New Zealand 10c mule
In the December 2015 issue of the Royal Numismatic Society of New Zealand’s journal, coin collector Jason Gray reported a new New Zealand mule - that of a New Zealand 10c reverse with a New Zealand one dollar obverse on 10c pieces dated 2004. New Zealand collectors had reportedly been setting aside 2004 10c pieces with double obverse rims for some time before the realisation that was it caused by the use of an incorrect die rather than a misaligned die (Harris, http://www.australian-coins.com/error-coins/new-zealand-2004-10c-1-dollar-mule/).
It is not the first circulating New Zealand mule - in 1967 numerous 2c pieces struck with an obverse die for The Bahamas 5c piece were discovered in circulation. The 2004 10c mule was much more subtle however - the design was identical but just 0.6mm smaller - and so went undetected until well after the withdrawal of the larger change and the introduction of smaller change in 2006.
Like the Bahamas 2c mule in 1967, the Royal Mint was also responsible for the 2004 10c mule. The mint sets were produced by the Royal Australian Mint however, and no mules have been reported in mint sets. The exact number of mules produced is unknown but the numerous die markers (Harris, http://www.australian-coins.com/error-coins/new-zealand-2004-10c-1-dollar-mule/) suggest that it was the product of a single die pairing and their apparent commonness would suggest that the accidental pairing went unnoticed for the life of the die: given this a likely mintage is somewhere in the low to mid hundreds of thousands out of the total 6,500,000 2004-dated 10c pieces produced. While many would have been destroyed when the larger change was phased out in 2006 it is likely that many examples of the larger change were also hoarded, so a reasonable survival rate is to be expected, especially in high grades because the mules only circulated for two years.
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