1988 Fifty Cent Pattern Die Trial

A small number of coin-like items resembling 50c pieces have been sighted on the market since at least the early 2000s and have been sold as pattern coins. They were publicised by Jon Saxton who believed perhaps 20 such pieces exist. The pieces appear to have been initially found or sold in England and have obverse and reverse designs that very closely resemble designs used on Australian coins. The Australian Capital Territory Coat of Arms design appears to have been used on the 1993 silver $10 coin and the Canberra Parliament House design appears to be modified from a design used on a 1998 silver proof $1 coin. Further research revealed that the pieces were reportedly struck at the Royal Mint for die testing (with the designs themselves not being of relevance to the tests) from dies created by a private mint in London (Saxton, https://web.archive.org/web/20181005220754/http://www.triton.vg/trial.html).

Andrew Crellin speculates that whoever struck the coins had a commercial relationship with the Royal Australian Mint given the use of their designs (Crellin, https://www.sterlingcurrency.com.au/198850cdietrial) and this seems reasonable - certainly the United Kingdom does not have any of its own dodecagonal coins, and Crellin's speculation that patterns were struck as part of a tender seem quite likely: the Royal Australian Mint outsourced the striking of some of its bronze coins to the Perth Mint throughout the 1970s; it outsourced the striking of much of its 1981 coins to the Royal Mint and Royal Canadian Mint and currently outsources its circulating planchet production to Poongsan Corporation in South Korea.

An example was sold by Sterling and Currency in early 2025 for $7,000: https://www.sterlingcurrency.com.au/198850cdietrial. The piece was graded SP65 by PCGS: https://www.pcgs.com/cert/38851181