You would think that a £1 coin would be worth exactly one pound.

But some lucky recipients of early or rare versions of the new twelve-sided coin could be set to cash in to the tune of hundreds of pounds.

The new twelve-sided currency started going into circulation on March 27th.

A number of unusual variants including early mock-ups or coins with errors are being offered to collectors on ebay for sums reaching up to several hundred pounds.

One expert said that anyone lucky enough to have got a rare variant could be "sitting on a future goldmine".

The new coins are designed to be hard to counterfeit - but that means there could be mistakes. Credit: PA

Among the most valuable are "dummy" coins sent out by the Royal Mint to businesses ahead of the official roll-out to allow them to adapt their money-handling machinery.

The coins - which are stamped with the words 'trial piece' - are not deemed legal currency but they are a rarity, which makes them highly attractive to collectors.

Alex Cassidy, from currency valuation site Coining It In, said that their value could rise even further in comments to The Mirror.

These new £1 trial coins are fascinating, especially considering the financial precedent of the £2 trial coins in 1994, which have since become one of the most sought after collectable coins in Britain. If these new trial coins turn out to be as valuable as 1994’s, then anyone who gets their hands on them now could be sitting on a future goldmine.

Alex Cassidy
Some coins are already selling online for hundreds of pounds. Credit: PA

Also on the list are special edition "proof" coins produced by the Royal Mint in precious metals.

Such coins were traditionally made as a final quality control before mass-production and are finished to a higher standard than normal currency.

These are not cheap - a silver proof coin sells for £75 while a gold version is on offer for £950.

However, some experts believe they could be a good investment.

Coins with errors on them could sell to collectors as rarities.

Mistakes such as an incorrect date or a misaligned image could all add to the value for collectors.

Mr Cassidy said the complexity of the new coins, with an image that covers both a silver-coloured centre and a gold rim, means there is more potential for mistakes.

Any error could mean that a £1 will sell for much more.