The 20p coin that could make you a mint!

Have you ever noticed something particularly unusual about one of your coins? Perhaps a missing date, denomination or an error in the design?

Well, that’s what happened to one collector who noticed something unique about their 20p coin…

A ‘spectacular error’

The 20p in question was minted in 1990 for a British overseas territory, and was sold as part of a set. However, instead of having the usual cupro-nickel finish, it was struck on a copper-plated blank intended for a different country.

The 20p error coin
A ‘spectacular error’ occurred on this 20p coin
Credit: SWNS

Collector, Alun Barker saw this unusual coin listed on eBay in December 2017 and bought it for just £50. But he was pleasantly surprised when, just a month later in January 2018, the coin was confirmed as a genuine error by The Royal Mint, who issued a certificate of accreditation. They also confirmed it was the only known 20p in existence with with error, making it one of a kind!

Exceeding expectations at auction

Alun decided to have the coin valued by specialists, Tennants Auctioneers, who initially estimated it could fetch as much as £1,200 at auction. However, when he decided to part with the coin in August 2023, Alun was astonished to find out it had sold for a whopping £1,400!

Tennants Auction Centre
Tennants Auction Centre, North Yorkshire
Credit: tennants.co.uk

Not the first rare 20p error…

The ‘Bronze 20p’

In 2017, collector David Crosier found a 20p coin with an unusual finish, which he assumed to be bronze plated. He sent the coin to The Royal Mint to check, and after x-ray fluorescence spectrometry, they confirmed it was a genuine minting error.

The 'bronze 20p' with a 20p and 1p from the same years
The ‘bronze 20p’ with a normal 20p and 1p from the same year

Somehow, a 1p blank had made its way into the presses and a 20p was mistakenly struck onto it.

Find out more about this extremely rare error coin >>

The undated 20p

Considered by many as the ‘Holy Grail of change collecting’, the undated 20p is undoubtedly at the top of most serious collectors’ wish lists. In 2008, an unknown number of 20p coins were released into circulation without a date on either the obverse or reverse. This followed a die mix up after the new Royal Shield design was introduced.

Undated 20p reverse and obverse
Undated 20p reverse and obverse

The Royal Mint confirmed this was the first time in over 300 years that a coin had entered circulation without a date, making it extremely sought-after by collectors. They also confirmed that, whilst exact quantities are unknown, no more than 250,000 of these undated coins made it into circulation.

These coins have been listed on the secondary market with a value as high as £10m, however you should always check the sold listings on secondary market sites to see how much collectors are actually willing to pay for a coin.

Our latest eBay Tracker shows that the undated 20p is currently selling for around £52.

Find out more about the undated 20p >>


Have you ever found an error coin in your change? Let us know in the comments!

Is your H.G. Wells £2 coin worth thousands? How to spot if you’ve got an ‘error’ coin!

Every keen collector knows that it is worthwhile paying close attention to the small details of your coins – it’s the only way you can ever hope to spot an error. 

From edge inscription mix ups to inverted effigies, there are a few stories that crop up more often than not. However, recently, a couple of ‘error’ stories have cropped up, that Change Checker really think you should pay attention to – involving an H.G. Wells £2 and the Technology £2…

Stay tuned as we take a closer look at these ‘errors’ and help you determine if your £2 coin is a genuine rarity!

H.G. Wells £2 – Blank ‘Error’

H.G. Wells £2 Blank ‘Error’. Source: The SUN.

This £2 coin was issued as part of the 2021 UK Commemorative Coin set and it marks the 75th anniversary of the death of science fiction novelist, H. G. Wells.

With the clue in the name, this bi-metallic coin is made up of a combination of a silver coloured cupro-nickel disc and an outer yellow nickel-brass ring.

In the case of this H.G. Wells £2 coin however, it appears that the blank used has a thicker yellow ring, much wider than what we’d see on normal £2 coins.

H.G. Wells £2 Blank ‘Error’ comparison. Source: The SUN.

When striking £2 coins, the first step is to punch a hole through a blank planchet to create the outer section. The inner core is taken from a different metal, sized to fit inside the outer ring.

There have already been estimations that if this coin was to be sold at auction, it could fetch over £1,000! We’re going to be eagerly awaiting confirmation from The Royal Mint whether this error is genuine or not. Nonetheless, it certainly makes for interesting collecting!

This coin is yet to be individually issued, so any ‘error’ versions will have come exclusively from the 2021 UK Annual Set. It’ll certainly be interesting to see if any other stories crop up after the coin’s individual issue….

Whilst there are no identical examples to compare the H.G. Wells £2 ‘error’ to, there have been previous instances of the inner and outer sections of £2 coins not quite matching up:

Clipped Planchet

In the above image, the inner core was punched out from the end of the sheet of metal used for blanks, forming a straight or ragged edge clip.

Whilst this also occurs with monometallic coins, the pairing with an outer ring exposes a large gap which is much more noticeable.

The Royal Mint strike millions of coins each year so it is inevitable that variances will occur during the striking process and can’t always be picked up during quality control, despite the fact that this particular coin would weigh less than the standard 12g £2 coin.

Off Centre Inner Core

The inner core of this coin hasn’t been united properly prior to being struck, resulting in an off centre inner core.

Due to the way the inner and outer core are struck together with the two metals being lined up and then fused together during striking, a misalignment will mean that the inner core spills into the outer ring, as seen in the image above. There might also be a gap between the two metals on the opposing join.

Faulty Outer Ring

This particular mis-strike, shows a faulty planchet or outer ring, where the inner core is exposed.

In the image above, you can actually see the specific engineering design features where the inner core is grooved to help the metal flow bond to the outer ring and fuse during striking.

Similar to the first mis-strike we looked at, this could be caused by a clipped planchet, this time created when the outer ring was punched, however coins like this may also be caused by tampering post striking, for example by fakers trying to replace the inner core of a £2 with another coin to pass off as a rare error.

Bronze £2 Error

2010 ‘Bronze’ Technology £2. Send to Change Checker by Amin.

The ‘Monometallic’ £2 is described as the Holy Grail of bimetallic ‘errors’ and is the result of the nickel-brass £2 blank not having the inner core section punched out before being struck.

This means that the £2 coin is made from one full piece of nickel-brass, completely contrasting the very idea of a bimetallic coin.

A 2007 monometallic £2 was verified by The Royal Mint and in the email confirming the mis-strike it was mentioned that they had only seen 4-5 similar coins before.

However, in 2021, Change Checker was contacted by a collector called Amin who informed us that he had found this exact error coin but with a 2010 date.

After sending details of his coin to The Royal Mint for further information, it was confirmed to be genuine error as a result of the minting process.

Letter sent to the collector from The Royal Mint confirming it’s genuinity.

This rare striking error is highly sought-after and coins have achieved extraordinary prices in private sales and auctions.

Whilst information of this coin’s sale has remained private, it’s certainly a very interesting story and we imagine the collector can expect to see a very impressive return on this coin…


We look forward to the individual release of the HG Wells £2 later this year and will certainly be keeping our eyes peeled for any unusual looking variations!

Have you ever come across any of these £2 error coins in your collection?

We’d love to know! Comment below.


Secure the 2021 UK Commemorative Coin Set – featuring the H. G. Wells £2!

Secure the 2021 CERTIFIED BU Commemorative Coin Set, featuring the 2021 UK H. G. Wells £2 for JUST £40.00 (+p&p) today >>

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