Regardless of their date and design all square kookaburra coins are rare. Leaving ultra-rare nickel and silver strikes aside, the 1920 cupronickel halfpenny tops the rarity bill. If you spot one at the next bourse for under a hundred grand, happily pay the money, grab the coin, and run.

Noble Numismatics sold an example at auction in late July for $238,000, plus 15 percent commission. It was the finest of two 1920s known to be in private hands.

Other prices paid at Nobles in July were $55,300 for a 1919 Stokes pattern penny, and $62,000 and $58,000 for two different types of 1921 Melbourne-struck pennies, the last having been owned by Buddy Ebsen. A 15 percent commission needs to be added to both prices.