An ultra-rare 50p coin could be worth 4,000 times its face value due to an unusual marking - and you could have one in your pocket. He said: "This is usually just worth face value unless you have a rare rotation error version. The 2009 Athletics 50pReleased in larger quantities in 2011, the Athletics 50p coin saw approximately 2.2 million copies enter circulation. Coin collector reveal value of every Olympic 50p coinThe 2011 Aquatics 50p Error CoinIn his final example, he shares the most lucrative coin yet. This coin holds a small but crucial error that makes it ultra-rare, meaning you can bank 4000 times its original value.