The challenge was to maintain a monetary circulation in settlements devoid of exportable commodities, from which the currency was leaving with the foreign merchant ships. The Spanish silver coin worth eight reales dominated these maritime transactions. The British idea was to transform these coins by providing them with a higher local value than the original in order to prevent them from leaving the territory for melting.
In November 1812, the British Government sent to Macquarie 40,000 coins of eight reales. Their delivery from Madras on a ship of the East India Company was successful.
The Spanish piece is punched. The outer ring and the detached core got an additional strike in the name of New South Wales at the date of 1813. The hollowed ring valued at five shillings is named the holey dollar while the central part valued at 15 pence is pejoratively nicknamed the dump. The freed convict to whom this operation had been entrusted was a good worker: almost all 40,000 pieces were processed.
The new currency was declared legal by Macquarie but it was not uniform because the origin of the coins was varied. The most prestigious for a collector of today are the holey dollars struck on a Madrid coin. According to the Australian press, one of them was sold for AUD 550K in a private sale in early May 2015.
On July 28 in Sydney, Noble Numismatics sells a holey dollar struck on a 1792 coin of eight reales from Mexico City, lot 1382 estimated AUD 350K, and another example on an 1808 Lima coin, lot 1383 estimated AUD 180K.
Here are the links to the article posted by Numismatic News and to the website of the auction house.