20 Ouguiya

Mauritania's currency has operated outside the CFA franc zone since independence in 1973, when the ouguiya replaced the CFA franc at a rate of 5 ouguiya to 1 khoum — the khoum being one-fifth of an ouguiya, making Mauritania one of the very few countries whose subunit is worth less than one-fifth of the base unit by design. The nickel plated steel composition of this issue replaced an earlier nickel-brass version, a cost-driven change that also slightly altered the coin's magnetic properties and surface character.