Do you have $4,000 in your pocket? How to spot a unique batch of $1 coins

A coin from a rare batch in the year 2000 is being sold at auction for more than $4,000.

Coin collectors are bidding for a unique $1 coin called a ‘mule’ through auction site The Purple Penny.

The mule is a hybrid of a 10 cent piece and a $1 coin and was in production at the Royal Australian Mint for a year before the mistake was discovered.

The coins are thicker than a regular $1 coin, with a double rimmed edge and a picture of the Queen on the back.

A rare ‘mule’ coin (pictured left) is being sold in an online auction for more than than $4,000

‘The mule was made when a technician at the Mint in Canberra accidentally paired the mob of ‘roos dollar reverse with the Queen’s head obverse, normally used for the 10 cent piece,’ the Australian Coin Collecting Blog reads.

The mule is being offered for $4,250 and is described by the auctioneer as ‘the nicest we’ve ever seen’.

‘Easily in the top 10 known coins of this type,’ the description reads. ‘Almost impossible to improve on and represents excellent value.’

Steve Troha from Town Hall Coins and Collectables estimated there would be around 6,000 of the mule coins in circulation.

He previously told Daily Mail Australia the majority of the coins appear to have been sent to Perth.

‘The first place they were discovered was the Burswood Casino [now Crown Perth],’ he said.

The coins are thicker than usual and heavier, with a double rim on the outside and are being offered for $4,250 (pictured)

The coins are thicker than usual and heavier, with a double rim on the outside and are being offered for $4,250 (pictured)

‘A gentleman who used to work there and had access to the coins and went through them and supposedly he found 300 to 400 of them just through the casino – that’s when it exploded in popularity.’

Mr Troha said the coins initially sold for $300 each but their value increased with their publicity.

‘I wouldn’t call it a rare coin, I would call it a scarce, very well publicised and known coin,’ he said.

Tiny minting errors on ordinary coins are highly sought after by collectors but many are going unnoticed because people rarely check for them. 

A tiny 5c piece from 2007 accidentally made with the Queen’s head on both sides was sold for $3000.

Coin expert Matthew Thompson said that particular minting mistake made the double-headed coin a rare ‘double-obverse’ that can be worth thousands of dollars in good condition.

‘The last one I sold was for $3500,’ Mr Thompson told Daily Mail Australia.

Numismatist Matthew Thompson from Town Hall Coins and Collectables with a rare double-stamped $2 coin that is worth $3000 due to a mistake by the mint during manufacturing

Numismatist Matthew Thompson from Town Hall Coins and Collectables with a rare double-stamped $2 coin that is worth $3000 due to a mistake by the mint during manufacturing

‘That one was in top end condition and so was worth thousands. One in really poor condition, you’d still be looking at a few hundred for,’ he said.

Mr Thompson said most people don’t check their coins and pass on rare coins worth thousands of dollars by accident.

Others are keen to inspect every coin in their change jars, which is a process called ‘noodling’.

‘I’ve done it before if I’ve a bag of coins or change jars. If you just spend a bit of time going through them it can certainly pay off,’ he said. 

Sometimes coins get clipped during the minting process when the discs are not ejected properly along the conveyor belt during the manufacturing process.

The blank disc can also get double-stamped by the high-pressure die. 

This double-headed 5c piece from 2007 is one of the rarer minting errors. A coin in really good condition can sell for about $3500, while those in poor condition still fetch a few hundred

This double-headed 5c piece from 2007 is one of the rarer minting errors. A coin in really good condition can sell for about $3500, while those in poor condition still fetch a few hundred

‘People don’t expect institutions like the Mint to make mistakes,’ he said.

‘But from time to time things can go awry.  If you see mistakes on a coin, if you have something interesting, odd or out of place, then other people are likely to find it interesting, too – that’s why people collect.’

Mr Thompson noted the $1 mule coins held exceptional value.  

‘If you see two rings on your dollar coin, it could be worth a few hundred or up to $4,000 in really good condition,’ he said. 

A more common $1 variant is ‘rabbit ears’ on the hopping kangaroos, which can make a coin worth up to $30, depending on condition. 

Detecting Downunder, a Facebook page run by coin collectors, said the recurring fault can be found on $1 coins from the years 1984, 1985 1994, 1998, 2000, 2006 ,2008, 2009, 2010, 2013, 2015 and 2016.

Detecting Downunder said this common 'rabbit ears' fault on the $1 coin can be worth up to $30

Many people reported finding 'rabbit ears' faults on their $1 coin in change

Facebook page Detecting Downunder said this common ‘rabbit ears’ fault on the $1 coin can be worth up to $30 in good condition. Many people have reported finding it in their change

Rare double-stamped $2 coin obverse (head side)

Rare double-stamped $2 coin reverse (design side)

The blank disc of this $2 was double-stamped by the high-pressure die during manufacture

More than 1900 excited treasure hunters commented on Detecting Downunder’s post, some of which had found more than one.

‘Found mine just a week ago in my change from a train ticket,’ wrote Jual Robert Butler.

Detecting Downunder also reported a rare 20c piece made in 1966 with a wavy baseline fault on the number ‘2’ is now selling for up to $2000.

Although the Mint made 58.2 million 20c coins that year, only a few of them had the unique wavy baseline, making the faulty coins valuable to collectors, Detecting Downunder wrote on Facebook.

‘If you happen to find one of these little beauties, it could be worth big money as these coins are currently selling for between $350 and $800 EACH on eBay, with one at $2000, and they’re only getting more valuable each year,’ Detecting Downunder wrote.

This rare 20c piece made in 1966 with a wavy baseline fault on the number '2' is worth up $2000. The bottom of the '2' is usually straight

This rare 20c piece made in 1966 with a wavy baseline fault on the number ‘2’ is worth up $2000. The bottom of the ‘2’ is usually straight 

The way to spot a wavy baseline fault is to look at the bottom of the number ‘2’ on the playtpus side of the coin.

On a normal coin both the top and bottom edges of the bottom of the ‘2’ are straight.

The faulty 1966 coin has a wavy top edge on the base of the ‘2’ that is clear to see, while the bottom edge remains straight.

Many people also collect Australia’s pre-decimal currency, and while copper pennies are common, there are some years you should look out for.

Mr Thompson advised people sitting on a bag of pennies to be on the lookout for 1925, 1930 and 1946 years that can be worth a little or a lot more.