In hidden vaults across the country, the US government is building a stockpile of $1 coins. The hoard has topped $1.1bn - imagine a stack of coins reaching almost seven times higher than the International Space Station - and the piles have grown so large the US Federal Reserve is running out of storage space.
Americans won't use the coins, preferring $1 notes. But the US keeps minting them anyway, and the Fed estimates it already has enough $1 coins to last the next 10 years.
And at the current rate, the inventory will grow to $2bn (£1.3bn) by 2016, the Fed estimates.
The coins began to pile up in 2007 when a law went into effect creating a new series of $1 coins commemorating dead US presidents.
Already stamped into millions of pieces of eight-gram, manganese-brass alloy are presidents no-one even remembers anymore, like Franklin Pierce, and ineffectual executives like James Buchanan, whose incompetence historians say helped lead the US to civil war.
Congress passed the law creating the coins despite evidence that Americans never liked the $1 coin in the past.
In a 2002 report, for instance, the investigative arm of Congress described "public resistance to begin using the dollar coin" despite a three-year, $67m (£42m) effort to promote the previous series.
Since the presidential coin programme began, the US government has spent an additional $30m to promote them but they still have not taken hold.
"We have tried every major idea that we can come up with, with limited success," US Mint Director Edmund Moy told a congressional panel last month.
US officials say a peculiar set of factors have hindered public acceptance of the $1 coin.
"Americans are creatures of habit," Mr Moy told Congress. "They are very used to using the bill. They're not used to using coins in regular retail transactions."
The US Mint has also identified an economic "awkward moment" in retail transactions involving the $1 coin. The buyer is afraid the cashier will reject the coin and cashiers are afraid buyers won't accept them in change, so both are disinclined to try.
Mint and Fed officials have also identified a vicious cycle.
Retailers will not stock the coins because they do not see consumers using them, while consumers will not use the coins because retailers do not stock them.
http://www.bbc.co.uk/news/world-us-canada-10783019
The circulating British one pound (£1) coin was introduced on 21 April 1983 to replace the Bank of England one pound note, which ceased to be issued at the end of 1984 and was removed from circulation (though still redeemable at the Bank's offices) on 11 March 1988.
The Australian one dollar coin was first issued in 1984 to replace the one dollar note then in circulation, this coin seems to be the most circulated denomination in Australia.
