At the time of decimalisation in 1971, the United Kingdom Crown coin (equal to 5 shillings) was redenominated as a 25p coin and pieces struck prior to 1990 - all the way back to 1818 - continue to be legal tender for that amount. The old denomination had been a regular circulating coin in the 19th century, but in the 20th century it became more of a commemorative denomination.
The Royal Mint continued issuing commemorative coins in the same format - using the traditional coin dimensions, but in copper-nickel. These were initially also denominated as 25 pence but the "Crown" was changed in 1990 to a commemorative £5 (five pound) coin, having the same dimensions and weight but with a face value twenty times as great.
The denomination is used to mark special occasions, usually royal in theme, rather than for use in general circulation. Although not circulating, these coins are legal tender.
This commemorative £5 Crown-sized coin is part of an 18-coin collection issued by the Royal Mint for the London 2012 Summer Olympics.
The 2012 Summer Olympics, formally the Games of the XXX Olympiad and commonly known as London 2012, took place in London and to a lesser extent across the United Kingdom from 25 July to 12 August 2012.
A Celebration of Britain is a collection consisting of 18 Crown-sized coins denominated as £5 which were released one at a time, every 28 days - so that the first six are dated 2009 and the last twelve are dated 2010. All feature the London 2012 logo, which is colourised on the reverse. The coins are grouped around three themes, with six coins dedicated to Mind, Body and Spirit respectively, and each theme having a differently coloured logo.
The Sir Isaac Newton coin is part of the Mind series and features Eduardo Paolozzi’s sculpture of Isaac Newton. Sir Eduardo Luigi Paolozzi (1924 - 2005) was a Scottish sculptor and artist. He is widely considered to be one of the pioneers of pop art. His 1995 sculpture "Newton", sometimes known as "Newton after Blake" is a large bronze which is displayed on a high plinth in the piazza outside the British Library in London. The sculpture is based on William Blake's 1795 print of Newton: Personification of Man Limited by Reason, which depicts a naked Isaac Newton sitting on ledge beside a mossy rock face while measuring with a pair of compasses or dividers.
The inscription, "Make not your thoughts your prisons", is a quotation from William Shakespeare's "Anthony and Cleopatra"; it can be seen as a message to Olympians and non-Olympians alike to strive to achieve beyond their expectations. | 
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