The Republic of Comoros, since 2001 officially the Union of Comoros, is an island nation in the Indian Ocean. It comprises three of the four main islands of the archipelago; the fourth isle is French oversea territory but claimed by the Union. The Comoros became independent from France in 1975; their population is mostly Muslim. The archipelago lay in the sphere of influence of Arabic and Persian sailors and traders, who began to settle on the islands in the 15th century. They preached Islam, built mosques and founded Islamic schools. When the first Europeans reached the Comoros in the 16th century, a Persian-Arabic ruling class was firmly established. In the 19th century the French began to take interest in the Comoros and by 1886, France had incorporated the four main islands into its colonial empire. This French piece of 2 francs dates back to the time of the French colonization. Today the Comorian franc is in use on the archipelago; it is divided into 100 centimes, yet centime coins are not issued.