It was once the 'rarest £1 coin in UK change', but now collectors are now being urged to be more vigilant about social media ...

Certain coins can fetch a hefty sum, even if it is one detail that makes collectors go wild for it. But it's no secret specific rare coins are more desirable than others, whether it's a 20p or 50p.

A rare coin could be the key to a small fortune, and it's been causing quite a stir recently. Whether it's the one penny piece hailed as the 'rarest in UK history' or an unusual 20p with a design flaw ...