YOU could have a 20p coin worth 300 times its usual value nestled among your small change thanks to a bizarre error by the Royal Mint.
The money-makers mistakenly released a batch of 20 pence pieces in 2008 without the year stamp.
The error makes them very rare - and increases their value to £60 each.
The gaffe occurred following a redesign of the coin over a decade ago.
There are thought to be up to 250,000 in circulation - meaning one could be in your back pocket.
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It’s well worth rummaging through your silvers to double-check if you have one of the rare coins.
Collectors are keen to get their hands on it as it was the first coin in over 300 years to enter circulation without a date stamped on it.
They have even been dubbed the "Holy Grail of change collecting" and some in mint condition have fetched more than £200 on eBay, although they typically sell for less.
TikTok user @thecoincollectoruk tipped off his followers about the potential windfall which they could be sitting on.
He explained: "Your normal 20 pence shield could be worth £40 to £60. On the back of the shield, there is a date at the bottom.
"However, in 2008 the Royal Mint released coins with no date by mistake. This is called a mule error."
A mule error is a term used to describe a coin with mismatched sides and is inspired by the fact the animal is a mismatch of a horse and a donkey.
The collector instructed Brits to examine their 20p pieces for a date, explaining they could be quids in if it is missing.
Normal coins display the date on the heads site, whereas it used to be presented on the tails side before the change in 2008.
However, these coins remain legal tender and still have a face value of 20p - although bidders may fork out much more for the rare coins.
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Dateless coins such as these are valuable as they are so scarce - and the 2008 blunder was the first of its kind since 1672.
We previously told how a dad made £200 selling a rare £2 coin that he found in his spare change.
Lucky Ben Mason, 26, was handed the 2011 Commonwealth Youth Games coin at his local shop last October.
Or take a look at our list of the most rare 10p coins in circulation - including an alphabet set worth 160 times its value.
