UK error coins are a fascinating and still fairly non mainstream side-line to regular coin collecting. Ignore the headline grabbing stories about error coins that are worth ‘a fortune’ that the tabloid/clickbait press push out. Most error coins are usually fairly low value and many minor errors can be picked up for just a few pounds. UK error coins, just like normal coins, are only worth what someone is willing to pay for them. That worth is strongly influenced by a number of factors including demand, rarity and the attractiveness of the error. An extra factor that plays a big role with error coins is their severity or unusualness.
Error coins have never really been a big deal in the UK until recently where interest in them has grown. An increase in people collecting coins has lead to more people looking closer at coins and noticing errors. People are now able to instantly share images of unusual coins on social media, prompting others to look for unusual coins. More suspected error coins are being discovered, shown and discussed. Some error coins end up being exposed in the press (and many aren’t actually errors at all!), usually as a result of people asking silly inflated prices for coins on eBay, that are completely utopian and where ‘sales’ at such prices are unverifiable and are very often not genuine or completed.
The recent increase in interest and higher demand for UK error coins has also prompted many unscrupulous people to create home made error coins that have clearly been manipulated and were not originally made like that. This is essentially post-mint damage and is something which has been especially rife with the new 12-sided £1 coin. Unfortunately, due in part to the demand fuelled by the tabloid stories and people not really understanding what they are buying, many have paid too much money for ruined coins that technically no longer even have a valid face value. To be able to spot shed-made ‘errors’ it’s important to understand how coins are made, especially the bi-metallic £2 and £1 coins (some more on that further down).
Here are some error types that I have observed on UK error coins over the years. There are other types of UK error coins and this list is not meant to be comprehensive. I’ll try to add pictures where possible. If you have an error coin that is not shown and can provide good quality images, please let me know.
Very common on modern (post approx. 2000) UK coins. Die chips are raised blob-like lumps on the surface of the coin. They are usually on a raised part of the design as opposed to on the lowest flat areas. Die chips on earlier coins are rarer, which seems to indicate to me that the Royal Mint procedure for striking coins has changed over the years. Perhaps they are saving money by using dies beyond their normal accepted lifetime or by not properly ensuring that coins are of high enough quality before they end up in circulation. Larger die breaks that also involve the rim are known as cuds. Die chips can be more interesting if they resemble something that looks intentional; see also die cracks, below.
The same principle as with a chip, i.e. the die that was used to strike the coin is damaged through excessive use. Instead of a blob, a cracked die results in a thin raised line on the surface of a coin. The line can turn into a larger blob if the faulty die isn’t changed and breaks further. The lines often pass through raised design elements like lettering and can sometimes run right to the edge of the coin. Cracked dies have resulted in recent coin anomalies where the crack happen to look like an extra feature, e.g. on the so-called ‘cat on mast’ 2015 Royal Navy commemorative £2.
I originally thought the 2016 Peter Rabbit 50p with ‘extra whisker’ was a die crack. This extra whisker is caused by a damaged die, but most likely damage from being scratched by part of the machinery called a feeder finger.
Blanks, or more accurately in most cases ‘planchets’, are pieces of shaped metal that haven’t been struck into coins. Higher denomination coins with edge lettering have the edge motto imparted onto them during a separate process and before they are struck. It is more common where blank £2 or old £1 coins are encountered, to find them with clear edge lettering but omitting the milling. The rim milling is imparted by the retaining collar at the same time as the design detail is struck between the two dies. Most blank planchets have a raised rim, as this is also imparted onto the disc before it gets struck between the dies in a process known as ‘up-setting’. Unstruck coins are unusual but can normally be obtained quite cheaply.
Blank coins with an edge motto that was only used for one particular coin design during one year only, and can therefore be properly attributed, are more desirable than a blank piece of metal that can only be attributed to a particular denomination.
Note that fake blank coins can potentially be man-made by smoothing down both sides of a normal coin. These are usually obvious to spot, as the surfaces often show tooling marks and/or are excessively polished. The thin layer of removed metal means that the fake ‘blank’ will weigh significantly less than a real one.
Note also, that 20p coin blanks are completely round. They are shaped entirely by the retaining collar during the striking process.
Round or shaped coin blanks are cut out of sheets of metal. This is done at high speed and sometimes something goes wrong and blank pieces of metal are produced that have been clipped on the edge (at least once) by the sharp press that cuts out the metal discs/shapes. When these irregular shaped blanks are struck into coins and released into circulation they are known as a ‘clipped planchet’ or ‘clipped flan’ error. The clip itself can range in size from being just a tiny, almost unnoticeable irregularity on the rim to being a fairly large crescent shaped chunk out of the coin. It is also possible (and much rarer) for a coin to have more than one clip, in different positions. When blank coins are cut too close to the edge of the strip of metal it results in a straight clip.
When the planchet (blank piece of metal) is struck between the dies, it is at the same time surrounded by a retaining collar which ensures the resulting coin is perfectly shaped. Either round or with ‘sides’ in the case of the new £1, the 50p and the 20p. For coins with edge milling the collar also features a negative ridged structure to impart the ridges (millings) onto the edge. It all happens very quickly. If a planchet isn’t positioned properly within the collar it results in an odd edge. Sometimes a raised lip, either partially or all the way around the coin or a smooth section of the rim where it should feature milling.
Coins that are not round are more susceptible to suffering from partial collar problems. The new £1 is by far the most commonly encountered coin with partial collar errors.
When a planchet is struck between dies without its retaining collar it results in an error known as a broadstrike. Without the collar, metal is able to flow outside of the normal constraints. Broadstrike coins weigh the same as normal coins of the same type, but are a little larger and thinner.
Sometimes when the blanks are not properly prepared, fragments of flat metal can splinter off from them, either before the coins are struck, or afterwards. This can result in what appears as hollow areas on the coin’s surface or in thin bits of metal that appear slightly raised. This kind of error is not particularly common on UK coins, but usually it’s viewed as ‘one of those things’ and lamination error coins are mostly not that attractive. There are some more extreme cases which are more desirable.
Are caused by different issues, but can result in a similar effect on coins. By far the most commonly encountered of the two on modern UK coins is ‘die clash’, which seems to have affected a number of 2016 Jemima Puddle-Duck 50p coins and some 2017 Isaac Newton 50p’s but can potentially affect any coin. Coins with die clash have elements – often just outlines – of the design from one side appearing on the opposing side. With the aforementioned Puddle-Duck 50p, the obverse has a faint outline of the duck and the reverse has a faint outline of the Queen. It is the result of the two dies coming together at great force with no coin-to-be between them and partially imparting their images on to the opposing die.
Ghosting, on the other hand, is caused by metal flow and is due to an imbalance of raised detail (or incuse detail on the dies) on each side of the coin. It was common on the early coins, particularly the pennies, of King George V.
Due to a number of possible causes during manufacture and sometimes environmental factors after a coin is circulated, coins can sometimes appear to be a different tone compared like for like. Some can have a streaky appearance, some appear much darker than normal. This can be curious and there are certain coins for which it seems to happen more often. It’s not really viewed as a serious fault.
Affecting mainly the new £1 coin but also some £2 coins – sometimes one or both sides have a dark coloured ring around the inner silver coloured part. This stain cannot be removed and is thought to be grease/gunk that was on the dies or planchet and has been burnt onto the coin due to the heat generated during the striking process.
When excessive grease or foreign matter gets into the dies it can result in missing detail on the finished coin. The most common result from grease in the die is very weak or partially missing lettering on the coin.
Some UK coins are made of a cheap steel core, plated with a more attractive metal that is less liable to corrosion. Since 1992 the 1p and 2p are made of steel, plated with a very thin layer of copper. Coins have been seen where this thin layer of copper is missing, most likely they were made that way and the blank piece of metal was missing its copper layer when struck. 1p and 2p coins that are silver coloured (and magnetic) are a fairly common occurrence as error coins go. To add confusion, it is actually possible to strip the copper layer from a 1p or 2p without adversely affecting the steel core, and with a resultant coin which looks very much like it was made that way.
As mentioned above, the 1p and 2p are steel, plated with copper. The 5p and 10p also have a steel core and are plated with nickel for a more attractive appearance. If the thin layer of external metal is compromised, dampness can enter. In extreme cases the coin can form large bubbles on the surface while quietly rusting from the inside. In the early stages this can also resemble a die chip (see no.1). It is likely that contaminants were present between the core and thin plated layer when the coin was made. It is also possible that the core has started to rust due to damage to the outer layer through use.
Very commonly observed on the Guy Fawkes £2 coin. It can, in extreme cases can have edge lettering that reads ‘PEMEMBEP PEMEMBEP THE FIFTH OF NOVEMBEP’ (the R’s resembling P’s). The tabloids made a big thing of it when it first came to light. That resulted in people speculating and paying far too much for such coins on eBay etc, before it all blew over. It is no longer considered a big deal. In fact Guy Fawkes coins with P’s instead of R’s are very common.
The edge motto is rolled onto the edge of the blank coin and either the raised tails of the R’s were broken, or the edge lettering was too weak and/or the edge milling too strong resulting in parts of letters becoming virtually lost within the vertical milling. Similar problems are noted with other letters on other £2 coin types and they don’t usually attract a premium.
This is not an error at all, it’s a twenty+ year old urban myth that still refuses to completely dissipate! In 1998 the Queen’s portrait was changed at about the same time as the introduction of the new bi-metallic £2. Lots of new £2 coins were struck in 1997 featuring the third portrait of the Queen, which show her wearing a necklace. Lots were also struck dated 1998 showing the fourth portrait of the Queen. Both types were first released in mid 1998 and a rumour spread that the £2 coins with ‘the Queen wearing a necklace’ were in some way special. I can remember my friend’s brother selling them to a bloke in his local pub for £20! They are very common and should never have been worth more than face value.
This isn’t really an error either, but is also something that comes up a lot. When a bi-metallic coin is struck, if something isn’t set up perfectly central, or the position of the outer ring and inner round part isn’t exactly as it should be, it can result in coins being produced with slight gaps between the two metal parts. This can result in design elements being missing. Usually the small beads around the rim of the silver part suffer most. In more severe cases, elements of the main design can also be lost. The Royal Mint do seem to be aware of the quality issues affecting bi-metallic coins as their higher-end coins are actually made differently and the metal joins tends to be much neater and the middle part almost always perfectly central.
Two examples of coins that often have common problems with the metal join are the 2006 Brunel portrait coin which often reads ‘TWO DOUNDS’ as the tail of the ‘P’ has been lost in the join of the two metals, or on the 2014 Kitchener WWI coin where the tail of the ‘Y’ from the ‘YOU’ above the date is also missing for the same reason. It’s unfortunate, but it is really down to the way the circulation coins are made at such speed and there will inevitably be imperfections.
No it isn’t! The edge wording orientation is completely random. It never used to be a thing. No one cared or even noticed it until the Sun reported (in one of the worst pieces of coin related journalism that I have ever read) during December 2016 that the edge lettering should be the right way up when the coin is held with the Queen facing upwards. I have no idea where they got this information. It was completely made up and even the Royal Mint must have been sick of the enquires. They published a piece online putting it straight.
It shouldn’t be possible, as the dies should be fixed in place and unable to move. Occasionally one of the dies that are used to strike the blank planchets into coins rotates slightly. It results in a coin that doesn’t have the tops of each side in the same opposing position. Die rotation errors are very rare for pre 2008 coins, but are known to exist for many modern coins. The more severe the rotation, the more desirable is the resultant coin. The most desirable die rotation error coins are ones where there is a 180 degree difference between both sides. Values for die rotation errors can vary from as low as a few times face value to hundreds or even (on very rare occasions) thousands of pounds, depending on the severity, rarity and how much people are prepared to pay to own it.
Slight die rotations on 7 sided coins (the 20p and 50p) are fairly common for certain types.
Doubled details, where some digits/letters or other design elements appear twice is most commonly caused by something known as ‘mechanical doubling’, or ‘machine doubling’. Mechanical doubling is caused when a coin is struck where there has been a simultaneous slight movement of a die, resulting in a double impression of design elements. Such doubling, although rare on UK coins, is considered a minor striking error and isn’t such a big deal in terms of desirability.
Very weak, usually raised shadows or faint hints at duplicate detail around design elements (mostly letters and digits) that tend to extend towards the rim of the coin is caused by die fatigue. This happens when dies are used well beyond their normal working life – each coin they have struck has taken its toll on the surface of the die and the repeated metal flow into the incuse die slowly wears out its detail. Often coins struck with worn dies can have letters and digits that appear fatter and less sharp. Worn dies that are not replaced can go on to strike many more coins with these features. This phenomenon is common and such coins are not considered valuable.
A much scarcer and much more pronounced form of doubled detail is caused when a coin is struck from a die that has been engraved with doubled detail in the first place. Doubled die coins are caused by a problem in what is known as the hubbing process, which is an earlier stage of coin production where master dies are created from a relief (raised) impression of how the coin side should look. The hubbing process that imparts the incuse (negative) detail on the master dies doesn’t happen once per master die and it is these multiple passes that can, if there is a slight slippage or movement, result in a master die with doubled features.
A recent example of this phenomenon occurs on the 2010 technology £2 coin, where most of the letters on the obverse are very clearly doubled – this has been seen on many 2010 £2 coins and is fairly common (for an error coin).
Something I have seen concerning some gold coins recently. The dies for proof coins and the dies for standard coins or for BU quality coins are quite different, even though they are of the same basic design. Proof dies are produced more carefully and usually have frosted raised details to contrast their mirror-like flat areas. Other types of coin finishes don’t have such a contrast between the flat and raised parts. Coins struck with mis-matching sides are caused by someone not paying attention. Resulting in coins with one side of an inferior finish to the other.
Basically a bi-metallic coins that looks a bit like a fried egg! Thought to be due to the pill shaped round part of the coin not lining up properly with the outer ring just before it’s struck. This causes it to be struck partially on top of the ring and not completely within it. The metal-on-metal means extra mass where it shouldn’t be and this is pushed out towards the edge sometimes leaving a gap between the two metals in the opposing join.
This error is known to be fairly common on the new bi-metallic £1 coin and on some 2015 £2 technology coins. It certainly isn’t exclusively a UK error though and occurs on many other foreign (e.g. Euro) bi-metallic coins.
Not strictly errors in the sense that something went wrong during production, but certainly a type of coin that probably shouldn’t have been produced and is often quite valuable. Withdrawn coins are coins with designs that for some reason were produced (often in low numbers), then changed or modified for the rest of the production run. The best known example of a recent withdrawn UK coin is the 2011 Aquatics Olympics 50p – very early coins sold in packages featured a very different reverse with extra lines on the swimmer’s face. This was changed and most of the coins sold in packs and all of the coins that were circulated featured a distinctly different design with less wave lines on the swimmer.
Another example of a withdrawn coin is a recent Falkland Isles 1oz bullion coin produced by the Pobjoy mint. This coin was withdrawn because the Royal Mint took issue with it having the word ‘BRITANNIA’ on it. They pointed out that no one apart from the Royal Mint is legally permitted to produce a silver coin featuring the word ‘BRITANNIA’. Pobjoy had to change it and released another version that completely omitted all wording on the reverse.
A brockage is a very rare type of error that is observed occasionally on older coins and is probably even rarer on new (decimal) coins. A brockage occurs when a coin is struck normally, somehow adheres to one of the dies and fails to eject. The next blank planchet is inserted and struck with the normal die on one side and with the coin that previously failed to eject on the other! The result is a coin (the brockage) which is normal on one side and has an incuse, often slightly weaker version of the same design on the other side.
The coin that originally got stuck in the die and failed to eject is known as a ‘die cap’ error. These are usually very expanded, a bit like a broadstrike (see also no.5B) with an irregular shape. Die cap errors are very rare.
Coins that are ‘double headed’ or ‘double tailed’ shouldn’t exist, at least not accidentally. The setup should make it impossible for the dies to physically be put in the wrong place. In almost all cases, doubled-sided coins with the same design on both sides have been created by manipulating two coins.
I have never personally examined a genuine double-sided decimal coin. I am aware that my predecessor at Rotographic did list a couple in previous editions of the book upon which this website was originally based. The coins in question were from the late 1960’s or very early 1970’s and were most likely created deliberately by Royal Mint employees to test out dies or some other element of production. A few double sided coins were featured in the Joanna Tansley collection, sold in 2005.
A mule is simply a coin struck from a mis-match of obverse and reverse dies, dies that should never have been used together but were incorrectly set up due to human error. There are a few modern well-known UK mule coins. The best known is probably the 1983 NEW PENCE 2p, made using the incorrect reverse die. Very well known and also quite common (for a mule) is the dateless 20p, which was made in 2008 as a result of someone using the incorrect obverse die from the previous 20p type. A more recent mule and so far very rare is the 2016 new £1 coin where the incorrect reverse die was used with ‘2017’ micro dates around the edge.
There are other mules including a 1994 gold proof £2 and a recent mix up with the dies for Lunar and Britannia silver bullion issues. The Isle of Man 1980 Christmas 50p with the incorrect obverse die that doesn’t state ‘Isle of Man’ is a known non Royal Mint mule. Not all mules are incredibly valuable, as the usual demand and scarcity factors play a large role in obtainable prices.
Occasionally coins are seen that have been struck slightly off centre due to mis-aligned dies, evident from an uneven rim with a thicker section on one coin side. Such coins aren’t usually of high value (it does depend on severity, as with all error coins). Coins that are struck very off-centre with missing detail on both sides are considerably rarer and are caused by the planchet being mis-aligned within the dies, rather than just a slight mis-alignment of one die. They often look spectacular enough to whet the appetite of many error collectors and for that reason tend to be of higher value.
Note that error coins known as ‘broadstrikes’ (see 5B) can also appear not properly centred.
My own personal favourite and the type of error that I seem to be drawn to the most! A coin struck on the wrong planchet. It happens when a planchet prepared for a completely different coin, (or in the case of some bi-metallic coins – an incompletely processed planchet) ends up somewhere it shouldn’t be and is made into a coin. Bi-metallic coins (the £1 and £2) are potentially more susceptible to being struck on a wrong planchet as the manufacturing procedure is more complicated and where there are more stages, there is more potential for something to go wrong.
Bi-metallic coins are by nature, made of two pieces of metal. A pill shaped central disc and a larger ring shaped piece are forced together at the same time as being struck with the dies. On rare occasions a ring shaped brass piece misses out on having a hole punched in it and manages to find its way in with the other correctly holed brass rings. I don’t know exactly how it happens or why the machines don’t notice that something isn’t right when an un-holed brass piece is rapidly inserted ready to be struck, but somehow it does sometimes happen and the result is a £2 or £1 coin made of a single piece of metal.
Bi-metallic coins struck for BU sets and packages are known to be forced together before they are struck. Perhaps monometallic error £1 and £2 error coins are all coins that were destined to become ‘BU’ or proof coins.
Other types of ‘off-metal strikes’ as they are sometimes known, are the result of a completely different blank intended for a different coin ending up somewhere it shouldn’t be and being struck with incorrect dies to what it was originally supposed to become. These incorrect planchets (or planchets in the wrong place at the wrong time!) are often other types of UK coins. The Royal Mint also strike coins under contract for many other countries. It’s very rare but can happen that ‘foreign’ blanks end up in the wrong machinery and get struck as UK coins.
Other factors can result in coins that look like they have been struck on wrong planchets – very stained or corroded coins (e.g. due the coin being previously buried underground) can sometimes appear to be a completely different colour/metal and can be mistaken for a coin on a wrong planchet. Also, 1p and 2p coins that are silver coloured are often normal coins that are missing their copper plating, see no. 11. Coins that have been manipulated and plated with another metal can also resemble a wrong planchet coin. Sometimes careful analysis is required.
Here are examples of coins struck on wrong planchets:
An incredibly rare type of error coin where a number of mishaps have occurred in the production process. These are the result of an already finished coin being processed once more as another or part of another (different denomination) coin. Resulting in a concoction that incorporates elements of two completely different denominations. The examples described here are both mixtures of a £2 coin and a 50p from the same year.
The example shown below has been confirmed as such an error by the US grading service PCGS. What appears to have happened is that a finished normal 50p (the 2006 VC cross heroic acts coin) has somehow ended up with the round brass discs that are normally holed to eventually make up the ring part of, in this case, the 2006 Isambard Kingdom Brunel £2 coin. The finished 50p has been holed along with the other brass discs and has moved along regular £2 production then been struck and combined with a regular pill shaped inner silver part. As the 50p outer ring is slightly thinner than a £2 coin, it doesn’t show much of the £2 detail and still clearly shows ‘FIFTY PENCE’ from its previous existence as a regular 50p.
The other known combination of an outer ring made from a 50p with a £2 centre is a 2014 coin. It features the centre £2 part of the Lord Kitchener coin and the outer ring from a standard shield-back 50p.
With man-made fake errors being common for certain coin types (the bi-metallic £1 and to a lesser degree, the £2). And with Chinese forgeries of error coins also known to exist it’s understandable that some collectors seek official confirmation. The Royal Mint do very kindly examine your UK error coins, for a small fee, and return them with correspondence describing the error (if the coin is a genuine error). Sometimes the letters can be very generic and do not go into any detail about the error type.
This is all very well, but is unfortunately open to abuse for two reasons. 1: The coin that the letter relates to is not photographed, so theoretically the error coin that the Royal Mint examined could be swapped. And 2: The letters are on Royal Mint headed paper, but are fairly easy to replicate. In fact I’ve seen a fake letter claiming to be from the Royal Mint describing a very dubious looking error coin. In a similar fashion, screen shots or print-outs of emails can also be faked!
The Royal Mint have some highly experienced coin experts and have a lot of expensive equipment. However, the letters they return are written by humans and they are not infallible. I’ve seen the text of a Royal Mint letter regarding a suspected error coin submitted by someone in 2015, where the coin in question had been, according to the Royal Mint, plated in nickel by someone post-mint. This was a conclusion that I did not agree with based on other factors, including the weight of the coin and other evidence relating to its appearance. Even experienced error collectors don’t always agree!
The error coin industry in the United States is massive in comparison to the UK. An alternative to authenticating errors via the Royal Mint is to send coins to one of the US grading services. The top two US grading services have very high standards with regards to authenticating and grading coins. These companies charge a higher fee for encapsulating (or ‘slabbing’) coins, so it’s best to only submit coins for which you are 100% confident of them being a genuine error. Encapsulated coins are guaranteed. If you buy any ‘slabbed’ coin and can prove that it is not as described on the label then the grading company can be made liable for its cost. When buying slabbed coins check the number and images online. There are known Chinese made fakes of coins in slabs!
As a general rule, serious collectors of UK error coins tend to have a very good understanding of the minting process. With a combination of that and the experience gained from seeing or studying similar error coins, they can usually identify a genuine error coin. Error collectors will often trade with each other without the need of any kind of official authentication. Trusting instead their own instinct and experience over above and beyond the knowledge of others.
Thank-you for reading this, any typos or other suggestions, let me know.
by CHP 16/12/17. Slight changes made 2/9/18. With some corrections/additional information by Jason Renaud and some proof-reading by Laura Davis, Sarah Grant and Candice Clews.