The British

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 decimal twenty pence (20p) coin – often pronounced "twenty pee" – was issued on 9 June 1982 to fill the obvious gap between the ten pence and fifty pence coins. It rapidly gained acceptance: as of March 2008 there were an estimated 2.3 billion 20p coins in circulation.

The coin is minted from a cupronickel

Cupronickel

Cupronickel or copper-nickel or "cupernickel" is an alloy of copper that contains nickel and strengthening elements, such as iron and manganese. Cupronickel is highly resistant to corrosion in seawater, because its electrode potential is adjusted to be neutral with regard to seawater...

 alloy of 84% copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 and 16% nickel

Nickel

Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

 (unlike the other 'silver' coins which are 75% copper, 25% nickel), weighs 5.00 grams and has a diameter of 21.4 millimetres.