Fifty Pence 2011 WWF, Coin from United Kingdom - detailed information

These circulating commemorative coins celebrate 50 years of the World Wide Fund for Nature (WWF).

The British decimal fifty pence (50p) coin - often pronounced 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, made it easily distinguishable from round coins both by feel and by sight, while its constant breadth allowed it to roll in vending machines.

The denomination was introduced in October 1969 when the 50p joined the 5p (shilling) and 10p (florin) coins in circulation, leaving only the three copper coins to be introduced on 15 February 1971 to complete the new series of decimal coins; unlike other coin types at the time though, the 50 pence coin was not equivalent to a pre-decimal coin - it replaced the old ten shilling banknote.

Twenty pence and fifty pence coins are legal tender only up to the sum of £10; this means that it is permissible to refuse payment of sums greater than this amount in 20p and 50p coins in order to settle a debt.

Coins issued in 2011 have now been in circulation for 13 years.