1981 New Zealand 5 cent/Canada dime mule
Various catalogues report a New Zealand a 5c piece that was struck with a New Zealand obverse muled with a Canadian reverse (p21, The John Bertrand Catalogue of New Zealand Coin & Banknote Catalogue, 2014). The catalogue itself does not specify which Canadian reverse: a Canadian 1c from the time had more or less the same diameter (19.1mm compared to 19.43mm for a New Zealand 5c piece) though it is reported that it was actually a Canadian dime/10c reverse die.
The circumstances in which it was struck and found are unknown but the Royal Canadian Mint struck New Zealand coins in 1981 - it is likely that the mule was a deliberate fabrication by mint workers. Other similar mules exist from the era.
There have been no known recent public sales of the New Zealand 5c obverse/Canada dime reverse mule.