The British pound coin as we know it will no longer be legal tender from October 15 – but you may have a rare quid that’s worth holding onto.

The current pound coin will be replaced by a 12-sided £1 coin which the Royal Mint will begin circulating next month.

So you’ll need to spend your ‘round pounds’ by the middle of October.

But if you have one of the rare variants of the humble quid – listed below – it could be worth up to £50.

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That’s according to changechecker.org which has listed 24 of the rarest £1 coins in British circulation.

Some are already worth £25 and their value is likely to increase one Britain switches to the 12-sided pound coin, The Mirror reports.

The rarest coin on the index, known as the Edinburgh City 2011 £1 coin, is selling for as much as £34 – more than thirty times its value.

While the 2011 Cardiff City £1 coin has sold for £20 and the London City 2010 coin is selling for £10.

Rare coins - Edinburgh City (2011)
Rare coins - Edinburgh City (2011)

Test versions, known as ‘proof coins’ are even more valuable with collectors. These are made by The Royal Mint and are struck at a lower speed with a higher finish.

Pound coins in order of scarcity:

1) Scotland: Edinburgh City (2011)

2) Wales: Cardiff City (2011)

3) England: London City (2010)

4) Scotland: Thistle & Bluebell (2014)

5) UK: Crowned Shield (1988)

6) UK: Rose and Oak (2013)

7) N.I.: Flax & Shamrock: (2014)

8) Wales: Daffodil & Leek (2013)

9) N.I.: Belfast City (2010)

10) Scotland: Lion Rampant (1994)

11) England: Millennium Bridge (2007)

12) N.I.: Flax: (1986, 1991)

Rare coins: Cardiff City (2011)

13) N.I.: Egyptian Arch Railway Bridge (2006)

14) England: Oak Tree (1987, 1992)

15) Scotland: Forth Railway Bridge (2004)

16) Wales: Dragon Passant (1995, 2000)

17) Wales: Menai Bridge (2005)

18) N.I.: Celtic Cross (1996, 2001)

19) UK: Royal Arms (1983, 1993, 2003, 2008)

20) Scotland: Thistle (1984, 1989)

21) Wales: Leek (1985, 1990)

22) England: Three Lions (1997, 2002)

23) UK: Royal Arms Shield (2008 - 2015)

24) UK: Royal Coat of Arms (2015)

Rare coins: London City (2010)

READ MORE: Why is the new £1 coin costing Kirklees a lot of brass?

Replacing £1 notes, £1 coins were first launched on 21 April, 1983.

Since then, a total of 2.2 billion £1 coins have been struck for circulation – but not all are still in use.

The last available figures for coins in circulation, published by The Royal Mint in 2014, suggest that 1,553,000,000 £1 coins are still in use today.