Australian Decimal Coin Weight Tolerances

How much does my coin weigh? This is a common question first asked when a coin seems not quite right. Is it an error coin? Is the coin missing design or a part of the coin? Does it feel lightweight or too heavy? Does it sound different when dropped on the bench? Does the metal it’s made from appear different to normal? A coins weight must be accurately measured on a scale ideally to 2 decimal places. This is usually done a jewellers scale.

A coin has a legal parameter that it fits with regard to weight. A normal weight can differ up or down and still fit into the tolerance for a genuine coin. It can be handy to know these allowable tolerances as we examine coins closely. This is why we’ve compiled this handy guide to help collectors out. Information derived from Australian Currency Determinations for legal currency.

Decimal Coin Tolerances

CoinStandard Design Metal Composition ShapeEdgeDiameter (max) mmThickness (max) mmWeight gramsWeight Tolerance gramsWeight Minimum gramsWeight Maximum grams
1 Cent (1c) Feather Tailed Glider 97% Copper, 2.5% Zinc , .5% Tin Round Plain 17.75 1.80 2.60 +/- 0.3 2.30 2.90
2 Cent (2c) Frill-Necked Lizard 97% Copper, 2.5% Zinc , .5% Tin Round Plain 21.80 2.20 5.20 +/- 0.3 4.90 5.50
5 Cent (5c) Echidna 75% Copper, 25% Nickel Round Milled 19.53 1.90 2.83 +/- 0.33 2.50 3.16
10 Cent (10c) Lyrebird 75% Copper, 25% Nickel Round Milled 23.82 2.30 5.65 +/- 0.49 5.16 6.14
20 Cent (20c) Platypus 75% Copper, 25% Nickel Round Milled 28.65 2.92 11.30 +/- 0.78 10.52 12.08
50 Cent (50c) Coat of Arms 75% Copper, 25% Nickel Dodecagon (12 sided) Plain 31.65 3.16 15.55 +/- 0.96 14.59 16.51
One Dollar ($1) Mob of Kangaroos 92% Copper, 6% Aluminium, 2% Nickel Round Interupted Milled 25.20 3.46 9.00 +/- 0.66 8.34 9.66
Two Dollar ($2) Aboriginal Elder 92% Copper, 6% Aluminium, 2% Nickel Round Interupted Milled 20.62 3.70 6.60 +/- 0.6 6.00 6.60

Posted in Collecting Coins

1969-1984 50c Struck on Underweight Split Planchet

As originally published in Australasian Coin and Banknote Magazine December / January 2020/2021

What Went Wrong -error coins that escaped the mint

Click image to enlarge

From 1969 to 1984 Australia used the Arnold Machin portrait of Queen Elizabeth II on coins and the distinctive 12-sided dodecagonal shape for the 50c piece. Missing design on this error coin means we cannot be more precise than to date it within this 16 year range.

Weighing in at 8 grams, just over half the mass of a standard 50c (which should weigh 15.55g) this coin is also only about half the thickness that it should be. This is apparent in the dramatic strike weakness seen across both sides of the coin. The legends are missing almost completely around the portrait and the numerals 50 on the reverse are barely visible. It’s interesting to note that weakly struck coins like this one often show better strength of strike in the centre of the coin radiating to more prominent strike weakness at the extremities.

Looking closely at the reverse we can see that the surface of the planchet shows parallel metal striations. This indicates that the cupro-nickel planchet had split in half prior to it being struck. Coin blanks are punched from sheets of metal rolled to the correct thickness. When the blank for this coin was punched out of that metal it contained a flaw in the material that ran parallel to the faces of the blank. At some point after the blank was cut but prior to the coin being struck the coin blank fell in two pieces.

This meant that an approximately half thickness blank was fed into the coin press and when struck considerable strike weakness occurred. This was simply because there was not enough metal to fill the dies for a fully struck coin to emerge.

Coin blanks do fall in half on occasion and it is more common to see a coin split after it was struck. This results in half a coin with one side having a striated appearance and the other side being struck with a design (obverse or reverse) as usual. It is very rare to see an Australian coin such as the 50 cent here struck on a planchet that split before the striking process.

Mark Nemtsas and Kathryn Harris own and run The Purple Penny coin shop in Adelaide and are passionate about error coins.

Posted in Error Coins

1961 Penny with Planchet Flaw / Hole

As originally published in Australasian Coin and Banknote Magazine November 2020

What Went Wrong -error coins that escaped the mint

Australian 1961 Penny with Planchet Hole Error

Not all coin errors that escape coin minting facilities are due to a failure in some part of the mechanical process of manufacturing coins. Sometimes the errors occur because of failures in the metallurgical processes that are required to produce the very metal that coins are made from. The image of the 1961 Perth minted penny shown has a clearly visible flaw caused by (for want of a better term) poor quality bronze.

Coins (generally) are made from metal blanks or planchets. Some of you might be wondering if there is a difference between a “coin blank” and a “coin planchet”, and indeed there is. However, that’s a subject we can cover another time and in this article we’ll use the terms interchangeably. Coin blanks are punched from strips of metal by a machine called a “blanking press”. Those strips of metal should ideally be of uniform width and thickness. Of course, the composition of the metal should also be consistent, but in the case of our 1961Y penny the metal strip the blank was punched from contained what is known as an “inclusion”.

On this coin the inclusion was a metal contamination that was probably an oxide, carbon, or something else like a nitride or a sulphide. The inclusion was embedded in the bronze and at some point while the coin was being made (or perhaps even after it was made) the inclusion has fallen out. On some errors of this type it is possible to determine if the inclusion fell out before or after the coin was struck, but in the case of this error we cannot do so.

A hole is visible right through this coin indicating the inclusion was a thick one. Errors like this penny with a hole through the planchet are very sought after and the bigger the flaw and wider the hole the more desirable they are. Sometimes you’ll see errors of this type with multiple inclusions and we’ve even seen some missing parts of the rim. They are an interesting error type and any serious error collector should look to add one to their collection!

Mark Nemtsas and Kathryn Harris own and run The Purple Penny coin shop in Adelaide and are passionate about error coins.

Posted in Error Coins

Rare Australian 20 Cent Coins

The Australian 20 cent coin was first minted in 1966 and in it’s more than 50 year history there are some rare Australian 20 cent coins that are sought after by collectors. In this article we’ll talk about the 4 rare Australian 20c coins you can look out for in your change and do our best to assign a value to them.

1. Australian 1966 London 20 Cent Wavy Baseline Variety

About half of the Australian 1966 20 cent coins were struck by the Royal Mint in London. For some reason one of reverse (tails) dies used in London was damaged and touched up resulting in a distinctive ‘Wave’ on the baseline of the 2 on the reverse of the coin. The so called ‘1966 Wavy Baseline 20 cent’ is the most sought after rare Australian 20 cent coin. Why? Because even a banged up one that has been circulating for 55 years can still be worth a couple of hundred dollars. If you’re really lucky you might find one in pristine condition in an old coin collection or money box, and that 1966 Wavy Baseline 20c could be worth $2,000 or more. How do you know if you have one of these rare 20 cent coins? Firstly your coin must be a 1966 and secondly it must have the distinctive Wave on the baseline of the 2. Checkout the image below, with the rare 20c you’re looking for on the left.

Wavy Baseline (Left), Regular Coin (Right)

Wavy Baseline (Left), Regular Coin (Right)

2. Australian 20 Cent Coins Struck on Wrong Planchets

Sometimes blanks for other coins get mixed up with twenty cent blanks and then a 20c is struck on these wrong planchets. For an especially rare Australian 20 cent coin you’d be super lucky to find one that is not only struck on the wrong blank, but is struck on a wrong blank from ANOTHER COUNTRY. This has happened several times during the lifetime of the 20c coin. Twenty cent coins from the 1970’s have been found struck on Thai temple token blanks and blanks of coins from Nepal. In the 1980’s a very small number were struck on scalloped Hong Kong $2 planchets. In this century a few have been found struck on bi-metal planchets possibly from Iran. How much is a 20 cent coin struck on a foreign planchet worth? Anywhere from several hundred dollars to several thousand dollars. See below a rare 2001 20 cent coin struck on a 10.7g bi-metal planchet.

2001 20 Cent on Bi-Metal Planchet

3. Australian 2001 Upset 20 Cent Error

At least one obverse die was loose during the production process of 2001 Platypus 20 cent coins which resulted in coins being struck with varying degrees of die upset. These hard to find upset die error 20 cent coins have appeared on the market with mostly small degrees of upset (less than 30°). They have popped up occasionally with large upset angles including the full 180°. What are they worth? The small upsets are worth perhaps $5-$10, while the big obvious upsets can be worth $100 or more! Certainly an Australian 20 cent coin to look out for.

Rare 2001 20c with 160 degree upset

4. Australian 1981 3 1/2 Claw 20 Cent

Industrial action at the Royal Australian Mint in 1980 and 1981 saw it outsource some coin production to the Royal Mint branches in Wales and Canada. Canada struck most of the 1981 dated 20 cent coins and included a die marker on the reverse of the platypus design to indicate they’d made the coin. The first claw of the left paw of the platypus is half the length giving the variety the name “3 1/2 claw” 20c. While not a rare coin it is quite hard to find in uncirculated condition. Circulated 3 1/2 claw 1981 20c are only worth face value, but uncirculated examples are worth $50+ and well worth looking out for.

1981 31/2 Claw 20 Cent Coin

Posted in Collecting Coins

World War 1 Australian Identity Disc for Patrick Donohoe

ID Disc for Patrick Donohoe, 1280

Seen above is an unofficial World War 1 AIF ID disc made from Egyptian 1917 (AH 1334) 5 piastres (KM#318.1). Obverse has been neatly skimmed inside the radius of the rim beads. The following inscription has been applied with skillful ‘wiggle-work’:

No 1280
EGYPT 1916 17 18

The disk spells the soldier’s name as “DONOHOE” while a search of as Australian military records shows Patrick Donohue served with regimental number 1280. Donohue, a native of Galway in Ireland living in Randwick, Sydney was 41 years old when he enlisted into the AIF on September 24, 1915 at Holdsworthy, NSW. Patrick was taken onto the strength of No. 5 Squadron, 2nd Remount Unit and shipped out to the Middle East on HMAT Orsova on 10 November 1915.

His records show no information from his shipping date until 10 October 1916 when he marched to the military camp at Moascar in Egypt from the Australian Reserve Depot in Helipolis, also in Egypt. No futher activity is noted until 5 October 1918 when he is moved to canteens at Suez, where he stayed for a month before moving back to the camp at Moascar. In July 1919 he marched to Port Said before shipping back to Australia on HMAT Delta, arriving in Melbourne in September 1919 and finally being discharged on 27 October 1919.

Donohoe or Donahue?

It’s worth spending some time looking at the spelling “DONOHOE” vs “DONOHUE” by examining the handwriting and signatures from the service records. There are two separate Enlistment Attestation Papers in the records that are clearly signed and filled in by different people. The “Application to Enlist in the AIF” form appears to be filled in by yet another person. Below you can see a comparison of the hand-writing and signatures. Clearly sometimes the name is spelled “Donohue” and others “Donohoe”. The ID disc shown here with “Donohoe” indicates the confusion continued during the man’s active service. Perhaps we can surmise from this and the different hand-writing that Patrick Donohue/Donohoe was largely illiterate.

Comparison of Signatures/Handwriting

One small clue as to the correct spelling can be found in an article from the Sydney Morning Herald dated 5 February 1948. The article mentions the Will of Dora Donahoe of Randwick in Sydney. The executor of that Will? Patrick Donohoe. And who does Patrick Donahoe/Donohue, service number 1280 list as his next of kin in 1915 on his enlistment forms? His sister, Dora Donahue of Randwick, Sydney. Conclusive proof that the correct spelling is Donohoe? No, not conclusive, but certainly compelling.


1.National Archives of Australia, (Date Unknown) Record B2455 for Donohue, P, Available: P Donohue Service Record, [Accessed 15 August 2021]
2. Sydney Morning Herald. Thursday 5 February 1948. Legal Notices. [ONLINE] Available at: [Accessed 15 August 2021]

Posted in Collectables and Ephemera

1976 50 Cents Double Struck Error

Originally published in Australasian Coin and Banknote Magazine October 2020

What Went Wrong -error coins that escaped the mint

Click image to enlarge

Your eyes are not playing tricks on you here, you are indeed seeing double when looking at this 1976 fifty cent coin. Life for this 50c started out just like most others, being struck as normal between an obverse (heads), reverse (tails), and collar die. Events after that point went awry! The coin failed to eject from the press, managing to move a mere 3mm before being struck for a second time. This out-of-collar 2nd strike overstruck and largely obliterated the majority of the first strike.

The first obverse strike is almost invisible under the second strike with just traces apparent around the date and legends and the back of Her Majesty’s portrait. On the reverse it’s much easier to see remnants of the underlying strike. Look at the disjointed appearance of the “50” and the clear remains of the bottom of the central shield. Closer examination of other parts of the reverse design make it apparent that there is a lot of flattening in the design from the second strike due to the placement of metal from the first strike.

Eagle-eyed readers may see that there is also a small strike-through (likely cotton or wire) at the base of Her Majesty’s hair. This coin is a fine example of a double struck Australian fifty cent coin and the authors would like to thank it’s owner for allowing the use the coin’s image in this article.

Mark Nemtsas and Kathryn Harris own and run The Purple Penny coin shop in Adelaide and are passionate about error coins.

Posted in Error Coins

1960 Florin Straight Partial Collar Error

As originally published in Australasian Coin and Banknote Magazine September 2020

What Went Wrong -error coins that escaped the mint

Click image to enlarge

At a passing glance this ‘quaternary alloy’ 1960 florin looks like most of the other 15.76 million minted with that date. This is one of those errors where close examination of the much neglected third side of the coin is required. When this is done it can be seen that this is a special coin indeed.

Australian florins have a reeded or milled edge, a feature originally designed in the middle ages to stop the coin being clipped. However, in more modern times it’s done to stop counterfeiting and to make coins more easily identifiable by touch. The coin edge is struck by the third die (the collar die) and on an Australian florin the edge reeding should extend from the obverse face of the coin to the reverse face. However, it’s obvious from the deformed edge of this coin that an error occurred when it was struck. The planchet only partially engaged with the collar die and thus the edge reeding hasn’t been applied correctly. Consequently, this error type is known as a ‘partial collar error’.

Examination of this particular example shows that the edge milling has been applied to about half the thickness of the coin and the other half is smooth. The milling is present adjacent to the obverse face and not present adjacent to the reverse face. Obviously, the smooth edge is where the coin blank failed to engage with the collar die, indicating that in this case the obverse die was the ‘anvil die’ and the reverse die was the ‘hammer die’. This error can be further classified as a ‘straight partial collar error’ as the transition between the struck / unstruck parts of the rim are parallel to the coin faces. When this transition is not parallel the error is typically known as a ‘tilted partial collar error’.

Mark Nemtsas and Kathryn Harris own and run The Purple Penny coin shop in Adelaide and are passionate about error coins.

Posted in Error Coins

2013 Purple Coronation Two Dollar Coin Value

2013 Purple Coronation $2 Coin

The 2013 Purple Coronation Two Dollar Coin (affectionately known as the “Coro”) is probably the second most popular coin of that denomination amongst collectors. While it’s not technically the first Australian coloured coin issued for circulation (the 2012 Red Poppy $2 coin holds that honour) it is the first coloured coin designed to withstand the rigours of circulation. The technology used to apply the purple paint on the 2013 Coronation $2 was different to that on the 2012 red poppy $2 and made the 2013 coin able to circulate without the paint being removed easily.

Being such a popular coin amongst collectors a very common question is, what exactly is the 2013 Purple Coronation Two Dollar coin worth? Before answering that question we must understand the two different forms it was issued in. A regular circulation coin was minted for general distribution via security companies with 995,000 of those coins minted. 34,967 special collector only “C” mintmark Purple $2 coins were issued in a capsule in a folder. These collector folders had a release price of $12.95.

As usual on this site we need to tell you a few things about the values in this article. Firstly, these values are RETAIL values, if you’re selling on eBay you might get these but remember eBay takes a cut. If you’re selling to a dealer expect to get about 20% to 50% less than the prices quoted. Second thing to realise is that the prices are current at time of writing (April 2021). To get an idea of values right now try checking out some of the sold ebay results for the different issues below:

2013 Purple Coronation (No Mintmark) Value

Right now an average circulated purple coronation $2 in EF or better grade might sell for $30-$40. A genuinely uncirculated example seems to fetch $50-$75. Of course genuinely uncirculated examples are not seen very often and we’ve seen very few in several years of collecting. This coin is one of those that gets a bit more if it’s uncirculated and graded by PCGS (see here for PCGS graded sales results on eBay). At time of writing an MS64 appears to be selling for about $100, MS65’s for about $120, and MS66’s for up to $175-$200.

Circulation purple coronations in original security bags or rolls seem to carry a premium over individual coins. 25 coin purple coronation bags have a value of about about $1500 (see here for Coronation $2 bag sales results on eBay). 2013 Purple Coronation coin roll values (security or Imperial / Cotton Co.) sit in a wide range from $1700 up to nearly $4,000. We’d advise caution when valuing rolls but we’d tentatively put a realistic retail value on purple coro rolls at $2750.

One other way the coin can be obtained is via the Royal Australian Mint in 5 coin bags that were branded by the Mint. Collectors were invited along to events held by the Mint in 2013 and your pocket change could be swapped for new shiny purple coloured coins in bags of five. These collectable little bags are worth $400-$500 each.

2013 Purple Coronation ‘C’ Mintmark Folder

2013 Purple Coronation ‘C’ Mintmark Value

A ‘C’ mintmark Purple Coronation $2 in a well kept ‘tri-fold’ folder might be worth $400-$500 right now, which is a couple of hundred dollars less than what they sold for in 2020. At the time of writing there were no eBay sold results for PCGS graded 2013 Coronation ‘C’ mintmark coins. However, we’d expect that those would sell for a very small premium above none-graded examples. Generally the quality of the 2013 ‘C’ mintmark coronations was excellent and third party grading seems to add little value.

Posted in Collecting Coins, Investing in Coins

2005 Mob of Roos $1 Coin – Struck 10% Off-Centre

As originally published in Australasian Coin and Banknote Magazine August 2020

What Went Wrong -error coins that escaped the mint

Click image to enlarge

This is just one coin out of a reported mintage of 5.792 million 2005 dated ‘Mob of Roos’ dollars sent into circulation. Without doubt this dollar certainly missed the mark. It’s been struck about 10% or 2-3mm off centre. This type of error coin is known as ‘off centre’ because some of the coin design is missing. On the obverse the top part of the letters “AUST” are missing. On the reverse the three outer kangaroos of the ‘Mob of Roos’ have ears that are partly missing.

How did this mis-strike occur? When the planchet was fed into the coin press it didn’t neatly fall into the collar die as expected and was subsequently struck off centre. The improperly seated blank is then struck unconstrained by the collar die leaving the entire coin out-of-round. Close examination of the base of the letters “AUSTRALI” shows the characteristic ‘V’ shaped indentations known as fishtailing. Fishtailing is an indicator of the metal flowing outward into the void where there was no collar to constrain the strike.

This is not a common error by any means but if you do have a dollar coin that is struck off-centre similar to the coin we’re discussing here then there’s a very high chance it’s dated 2005 as a number of these have been found. Why this many? That is uncertain, but perhaps one or two die pairs were setup incorrectly for the production run. Was there a fault with the coin press? Another possibility is that a group of Type I (un-rimmed) coin blanks were fed into the dies, this being another common reason for off-centre/out of collar strikes.

If you look closely at the cheek of Her Majesty you’ll see a tear shaped die chip. This die indicator is present on a number of similar 2005 ‘Mob of Roos’ errors such as partial collars, broad-strikes and off-centre errors. The authors note that other 2005 errors of a similar type are seen without this die indicator. More research is needed to understand if there were multiple die pairs involved in creating these errors or if it was one die pair deteriorating or malfunctioning through their production life.

Mark Nemtsas and Kathryn Harris own and run The Purple Penny coin shop in Adelaide and are passionate about error coins.

Posted in Error Coins

Australian Dollar Coins that are Worth Money!

It’s the dream of every Australian coin noodler to find that one coin that makes all the time, effort, and dirty hands worthwhile. One of the most commonly hunted denominations is the humble dollar coin. So what should you, the dedicated coin hunter, know what Australian Dollar Coins to keep your eye out for? This article will cover the top 4 Australian dollar coins that are worth money.

Year 2000 $1/10c Mule Found while Noodling

1. Mules

Mules are coins that are struck by coin dies that were not intended to be used together. There’s at least three mules in the Australian dollar coin series that are worth good money. The first is the legendary Year 2000 $1/10c Mule which if found in your change today (March 2021) would be worth a few hundred dollars. The other two mules to watch out for are the extremely rare 2014 and 2015 ANZAC $1 / 10c mules. Both of these were accidentally struck with ten cent heads dies, just a handful of each has been found and they could be worth thousands of dollars if you’re lucky enough to find one.

2. 1992 Mob of Roos Dollar Coin

The 1992 Mob of Roos dollar coin is the stuff of legends. For years the Royal Australian Mint website suggested that several thousand were minted but in reality almost none were or they were all destroyed. In all our years of tracking the error coin market we only know of two or three that have been sold, and those in the high thousands of dollars. So what’s the moral here? If you’re looking at dollar coins and you see one dated 1992 make sure you flip it over and check out the reverse design to see if you’ve got a coin worth real money!

Australia 1 Dollar 1984 Wrong Planchet Error

3. Dollar Coins Struck on Wrong Planchets

Those of you with even the most basic knowledge of coins will know that coins are struck on metal discs called blanks or planchets. Obviously it’s in the best interest of any coin mint that they be struck on the CORRECT blanks or planchets. However, sometimes they are not, resulting in what is known as a wrong planchet error. There have been several instances of this happening in the dollar coin series and each is worth a good chunk of change. A couple of key examples to look out for are the 1984 Dollar struck on a Ten Cent planchet and the 2009 Australian Mob of Roos Dollar Struck on Bi-Metal Planchet.

Australia 2001 Upset Centenary of Federation 1 Dollar Coin

4. 2001 Centenary of Federation Upset Dollar Coins

Make sure that you check each and every 2001 Centenary of Federation $1 coin to make sure the head and tails side are the same way up! For some reason during the production process of these coins the obverse (heads) die of one pair of dies became loose and a number (many thousands) were struck with the head/tails dies not correctly oriented. These are known as upset coin errors. These errors are not hugely valuable, but if you were to find one it would probably buy you a nice snitty at the local pub. Certainly worth enough to not want to throw back into circulation!

NOTE: The values in this article were current and approximate at time of writing (March 2021). To get a better gauge of values of these Australian Dollar Coins try checking recent auction results on sites like eBay or sold results from major Australian coin auction houses.

Posted in Coin News, Investing in Coins

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