The British fifty pence (50p) coin - often pronounced as "fifty pee" - is a unit of currency equalling one half of a Pound Sterling. It is a seven-sided coin formed as an equilateral-curve heptagon, or Reuleaux polygon - a curve of constant width, meaning that the diameter is constant across any bisection. This shape, which was revolutionary at the time of its introduction, makes it easily distinguishable from round coins both by feel and by sight, while its constant breadth allows it to roll in vending machines.
The first UK Fifty Pence coin was issued in 1969 with the classic Britannia reverse design by Christopher Ironside, which was superseded in 2008 by the Matthew Dent design for circulation coins.The denomination is also extensively used to issue circulating commemorative coins.
Beginning in 2009, the Royal Mint started issuing 50 pence coins for collectors - such as this one - which are not meant to be released in circulation, so are classified as Non-Circulating Legal Tender (NCLT).
The first UK Fifty Pence coin was issued in 1969 with the classic Britannia reverse design by Christopher Ironside (which was superseded in 2008 by the Matthew Dent design for circulation coins. Between 1969 and 1981, the denomination was given on the coin as NEW PENCE, which was changed in 1982 to FIFTY PENCE.
Beginning in 2009, The Royal Mint also started issuing 50 pence coins for collectors which are not meant to be released in circulation, so are classified as Non-Circulating Legal Tender (NCLT).
This coin is part of a 16-coin set featuring sixteen different 50 pence designs (of which this was the third) to mark 40 years since the introduction of the denomination. The UK 50p 40th Anniversary (1969 - 2009) Set was issued as copper-nickel proofs, silver proofs, gold proofs and gold piedfort proofs.
No 2009-dated coins of this type were issued into circulation. | 
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