The British decimal fifty pence (50p) coin – often informally 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. Its obverse has featured the profile of Queen Elizabeth II since the coin's introduction in 1969. Four different portraits of the Queen have been used, with the latest design by Jody Clark being introduced in 2015. The second and current reverse, featuring a segment of the Royal Shield, was introduced in 2008.