5 Ouguiya

Mauritania's ouguiya is one of only two currencies in the world not based on a decimal system — five ouguiya equal one khoum, an arrangement retained from the country's monetary restructuring at independence from France in 1973. In 2018, the country redenominated entirely, introducing a "new ouguiya" worth ten old ones, which makes coins from this 2017–2018 window transitional issues struck just before that reform erased the old unit of account.