monetary unit of Nigeria. The naira is divided into 100 kobo. The naira was introduced in 1973, when the country decimalized its monetary system and substituted the naira for the Nigerian pound (the country used the British pound sterling when it was a British colony), which was divided into shillings. The Central Bank of Nigeria has the sole authority to issue banknotes and coins. Coin denominations range from ¹/₂ kobo to 1 naira. Banknotes are denominated in values from 5 to 500 naira. Most of the banknotes contain images of previous political leaders important in Nigeria's history; for example, Sir Abubakar Tafawa Balewa (Balewa, Sir Abubakar Tafawa), Nigeria's first prime minister, is pictured on the 5-naira note, and Nnamdi Azikiwe (Azikiwe, Nnamdi), Nigeria's first president, is on the 500-naira note.