Time to check your change … do you have the 50 pence piece that’s worth up to £310 in your pocket?

The Royal Mint team has been at it again.

We’ve been working on a little story for the makers of all of Britain’s coins to find the rarest in circulation. We thought that the public might be interested to know about the history and story behind one of the coins in their pockets – and The Royal Mint are firm believers that the coins we carry around mean that we also carry about some of the history of our country – beautifully designed artifacts of national identity.

So, following some research and debate with The Royal Mint Museum, we discovered that the rarest circulation coin is likely to be one that was issued in 2009 to mark the 250th anniversary of the found of the Royal Botanic Gardens – better known as Kew Gardens – in London.

Now it turns out that there were just 210,000 of these coins minted (compared with compared the nearly 23 million with the shield of the Royal Arms in 2008 and 7.5 million of the Girl Guiding 50 pence in 2010). That means (by our estimations) that just one in 300 people in the UK is likely to have one of these rare Kew Garden coins.

So it was that, armed with all our findings – and what was a damnably fine piece of simple news-thinking in the first place – we went out to the media with the story.

The response was remarkable.

We’ve been in every national paper this morning with cracking pieces – we were page three of The Sun, the Daily Mail, the Independent and the i. What’s more, the Daily Mail made the story the second on its homepage. Placement doesn’t get better than that.

The web is awash with coverage from across the papers with the Daily Mirror, Daily Mail (er … twice), The Guardian, Independent,  Daily Telegraph (and Daily Telegraph pictures) and METRO. Then the money pages went a wee bit nuts for it, with pieces in Moneywise, MoneySavingExpert, ThisIsMoney.

Then there are the big news sites like ITV.com, Aol., Yahoo!, a spot of Huffington Post. And the regionals – from the Herald to the Journal to the Yorkshire Post to the Birmingham Mail to the Brighton Argus. Pretty much you name it and they covered it.

Quick. Simple. Effective.