Australia's first coin was a mongrel with a colourful history. Faced with a dire shortage of local currency, Governor Macquarie had the bright idea of buying 40,000 Spanish silver dollars, which at the time were minted in exotic locations such as Peru and Mexico.
He converted these to Australian currency by enlisting a convicted forger, William Henshall, to punch holes in the middle and stamp New South Wales, Five Shillings and 1813 around the inner ring.
Today we might call that an act of vandalism.
They soon became known as the Holey Dollar and, for most Australian collectors, owning one is the Holy Grail. Next year marks 200 years since the Holey Dollar went into circulation. About 300 of the coins survive, with maybe 200 in private hands, although some are more special than others.
One of the most notable is known as the Hannibal Head, a reference to the unflattering portrait of Joseph Bonaparte on the original Spanish coin. It is the only one known bearing this design and this, plus its exceptional condition, makes it one of the most desirable Holey Dollars.
It will be offered at the Eminent Colonials Auction in August through Coinworks, bearing the estimate of $450,000. Experts consider that a conservative figure.
The investment potential of Holey Dollars is demonstrated by the previous public appearance of this coin at a 1988 Spink auction. It had a $45,000 presale estimate on that occasion but didn't sell.
The managing director of Coinworks, Belinda Downie, suspects one factor was that there were 13 Holey Dollars listed at the auction.
''That was just too many,'' she says. ''The market wasn't ready at that stage.''
She has since heard that this coin sold privately after the auction for $40,500, a bargain in hindsight. She picked it up in 2007 for $260,000 and quickly on-sold it to a client.
Five years later and Downie is confident it will sell for more than $500,000; $600,000 is a possibility. In recent sales, three other examples have fetched more than $400,000. She sold one for $485,000 less than year ago.
Downie is used to handling expensive coins. In 2011, Coinworks sold a 1930 proof penny for an amount that she would only say was above the $1.5-million mark - a record result for an Australian coin. That coin was in mint condition.
The Hannibal Head Holey Dollar is rated ''nearly extremely fine'', remarkably good condition for a coin that was in open circulation in the early 1800s.
Some Holey Dollars are well worn but Downie says she still gets a buzz from handling such a historic coin. Curators' white gloves are required for those million-dollar proof pennies.
The Hannibal Head is the highlight of the Eminent Colonials Auction, which also includes an 1813 Dump. These tiny coins are what happened to the inner circle of silver that was punched out of the Spanish dollar. Originally worth a mere 15 pence, these are also in demand and the one listed is valued at $250,000.
Warren Joel is the guest auctioneer and for this special event there will be no buyer's premiums.
Coins of this calibre are now sought after by investors as well as traditional collectors. They can be included as part of a self-managed super fund (SMSF), provided they are kept in a safe and insured under the name of the fund.
The Coinworks' Eminent Colonials Auction is on at 7pm on August 27, RACV Club, 501 Bourke Street, Melbourne. The online catalogue is on the Coinworks website, coinworks.com.au.