One of the most popular areas in the “traditional” realm of Australian numismatics is identification and collecting of the different varieties of Australian pennies.
Nearly all of the penny varieties that have been identified and prized to date feature the obverse of King George V, and were struck in the approximate timeframe of 1919 and 1933.
It is fair to say that far less attention has been paid to the penny varieties that were struck after that period - they are less celebrated, despite their collector appeal or numismatic importance.
Detailed research by Dr Paul Holland, published in Volume 12 of the Journal of the Numismatic Association of Australia in 2001 (pages 39 - 44) demonstrated that the coin known as the 1955 Perth "Mule" penny was struck during between April 27 and May 15 in 1956 (not 1955 as the date might suggest), a time when the Perth Mint was transitioning from one master die type to another.
As the two dies used to strike this coin were not intended to be used together at the time they were produced, they have been designated as “mules” - hybrid coins from an unintended pairing.
Dr Holland has determined that just 392,000 pennies were struck with the combination of dies that he describes as Obverse 4 and Reverse D, described elsewhere as Obverse 9 and Reverse G.
When we consider the total mintage of 1955 Perth pennies as being 11,109,600, we can clearly see that the 1955 Perth penny mule is 28 ~ 29 times rarer than the standard 1955 Perth penny.
It is yet another interesting variety that dedicated penny enthusiasts can keep an eye out for.