As the introduction of the new, 12-sided £1 coin approaches, collectors are looking to complete their sets of the current coin before it's too late - and some are certainly worth more than a quid.

Collectors website changechecker.org has released a table ranking 24 of the current £1 coin designs in circulation, with many worth well over their face value.

While the most common coins - with a 'scarcity rating' of 1 - are only worth their face value, others, such as the Edinburgh coined with a rating of 1 are changing hands for up to £50.

The website said: "Up to now, change collectors have relied upon mintage figures for their indication as to which coins in circulation are the rarest. But the story is not that simple.

"The £1 coin has been in circulation since 1983. During that time a total of 2.2 billion £1 have been struck for circulation. But they are not all still in use.

"There are 1.5 billion coins in circulation but probably fewer than 800,000 of the rarest design.

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

"In other words, 650 million of the coins struck no longer circulate, presumably withdrawn over the years as worn or damaged.

"The majority of those 650 million coins are from the early issuing years, meaning that although some of those years may have high mintages, the actual number of coins available to collect from your change is far lower.

"In fact our research suggests that only a little more than half of the early years’ £1 coins are still in circulation.

"Far fewer if you’re trying to secure one in good collectable condition."

So check those pockets and those piggy banks - you could be sitting on a nice little investment.

Here's your guide to the £1 coins and how rare they are...