500 Ouguiya

Mauritania's 500 Ouguiya series has been quietly revised several times since the country's 1973 monetary reform replaced the CFA franc with the ouguiya — a currency whose name derives from the Hassaniya Arabic word for a unit of weight. The 2013 date places this within a period of gradual security upgrading across the BCM's note range, with G&D's Leipzig facility providing the production throughout much of that modernization cycle.

Pick 18 is not a scarce note, but the series attracts attention among specialists for the ouguiya's unusual subunit structure: one ouguiya divides into five khoums, making Mauritania one of the very few countries whose base currency unit does not divide decimally.