As originally published in Australasian Coin and Banknote Magazine April 2021

What Went Wrong -error coins that escaped the mint

Australia 1966-1984 2 Cent Off Centre Error

If you’re new to coin collecting or just new to error coins then the ‘off centre’ coin error is among the most instantly recognisable. As well as being distinctive, they are extremely desirable because it’s so obvious what has gone wrong with them! The coin in the image seen here is an Australian 2 cent that has been struck 40% off centre. 40% of the coin remains unstruck while 60% of the design is present. We’re not sure of the date (because the date is missing) but the Arnold Machin portrait of Queen Elizabeth II places it somewhere from 1966 to 1984.

This error two cent coin was produced when the blank planchet entered the coin press while the collar die failed to engage. The collar die is the third die that holds the planchet and if required, applies any edge milling. The coin blank was not located properly (perhaps due to the lack of the collar die engagement) and when struck was several millimeters away from where it should have been. This gave us our off-centre strike. How do we know the collar die was not engaged? Primarily because the coin is flat without any noticeable step in it.

What makes an off-centre strike a more desirable error to own? There’s a number of factors which of course include grade and condition. Another major factor is how far off centre the error is and generally the further off centre the more desirable it becomes. The final factor is the denomination as this usually dictates the scarcity of errors. In the Australian decimal series $1, $2, and 50 cent off-centres are the most sought after. This is followed by 20 cent, 10 cent and the remaining three smaller denominations more commonly found.

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

As originally published in Australasian Coin and Banknote Magazine March 2021

What Went Wrong -error coins that escaped the mint

Australian 1953-1964 Half Penny Die Adjustment Strike

The accompanying image shows an Australian coin, half penny in size and weight, that is missing almost all the design around the edges of the coin. It has almost no trace of the legends apparent. The keen-eyed observer may also note that the portrait of the Queen and the kangaroo are very weak and incomplete. Why is this the case? It’s a simple enough explanation, the coin was struck with a much lower pressure than that required to produce a fully struck up design. The next (and obvious question) is HOW did it get struck with such a low pressure? That’s a more difficult question to answer precisely. Before we address that we’ll look at a couple of other characteristics of this coin that gives us interesting insights into the coin production process.

Firstly, how do we know this error coin that escaped the mint is actually due to a low-pressure strike and not a filled die? The primary indicator is the consistency of the quality and strength of the strike across each side of the coin and when comparing the two sides to each other. Notice how both sides are (relatively) strongly struck in the centres and the quality of strike gradually weakens out toward the edges of the coin. Filled dies tend to show random changes in strike strength depending on where the die is filled while weak strikes show the gradual change in strike strength seen here.

Secondly, WHY does the coin appear more strongly struck in the centres and not struck at all around the edges? That’s because often coin dies are not flat! They are ever so slightly dome shaped with the highest portion in the centre and the lowest at the edges. As a result, extreme weak strikes like this half penny show the strike characteristics you can see so clearly here.

What is the name for this type of error? Typically, you’d see it labelled as a “die adjustment strike”. This suggests that it was produced deliberately during the coin press setup process and the die striking pressure was being adjusted or ‘dialled in’ to create coins that are properly struck up, but not struck so strongly that the life of the coin dies is reduced. Of course, if striking pressure was reduced accidentally (due to a machine failure for example) exactly the same type of error coin would be produced. Whether we call this handsome half penny a “die adjustment strike” or a “weak strike” it’s an impressive coin error well worth seeking out!

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

As originally published in Australasian Coin and Banknote Magazine February 2021

What Went Wrong -error coins that escaped the mint

Australian 1988 10 Cent Struck on 2 Cent Planchet

Leave an Australian copper nickel coin (5c, 10c, 20c, or 50c) lying on the ground for several months or years or perhaps bury it for some time and it will often tone a distinctive brown earthy colour. On first glance the coin shown here has this type of colouring and perhaps it would be spent by a member of the public without too much thought. This coin is quite different though, it is clearly uncirculated and shows considerable mint bloom, similar perhaps to a bronze coin. We knew it was something special and an XRF test confirmed that this coin was not struck on a cupro-nickel blank but in fact a copper alloy blank intended for two cent pieces.

The coin weighs in at 5.16g well within tolerance of the nominal weight of a two cent coin. This is exactly half a gram less than a regular 10 cent coin. Could a 2 cent blank be struck by ten cent dies? The diameter of a 2c is about 2mm less than a 10 cent, so yes, a 2 cent blank could fit into the collar die intended to mint a 10 cent coin and be struck. But of course, the lower mass and smaller diameter would give rise to key indicators in the strike of the coin. Are these indicators present? Yes, indeed they are.

The obverse legends in particular ABETH II of ELIZABETH II exhibit fishtailing of the lettering, this is a sure sign of unconstrained radial metal flow due to the small blank not filling the collar entirely prior to being struck. You’ll also note that the rim is not fully formed for about one third of the circumference of the coin. This is another sign that the blank was both undersized and underweight. Sadly scratches on the reverse are tell-tales that this coin may have failed to exit the coin press and was helped along the way by an eager mint technician with a metal tool of some sort.

Wrong planchet errors are always highly sought after by collectors. Wrong planchet, off-metal errors are more visually appealing because they are obviously the wrong colour. Underweight, wrong planchet, off-metal errors are even more desirable because of the distinctive qualities of the strike that help establish their authenticity. This 1988 10c struck on a 2c blank fits all these criteria nicely and as such is a very desirable coin. Eagle-eyed readers might have noted a small cud on the top lip of the Queen’s portrait. This may allow the fastidious collector to find a regular copper nickel 1988 10 cent struck from the very same dies as this spectacular error. That would be a fine pair of coins to own!

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

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

What Went Wrong -error coins that escaped the mint

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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.

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.

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.

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.