In 1973, coins were introduced in denominations of ½, 1, 5, 10 and 25 kobo, with the ½ and 1 kobo in bronze and the higher denominations in cupro-nickel. The ½ kobo coins were minted only that year. In 1991, smaller 1, 10 and 25 kobo coins were issued in copper-plated-steel, along with nickel-plated-steel 50 kobo and 1 naira. On 28 February 2007, new coins were issued in denominations of 50 kobo, 1 and 2 naira, with the 1 and 2 naira bimetallic. Some Nigerians complained that the weight of the ₦2 coin especially how heavy it is when there is a lot of it . The CBN announced that the old coins are to be replaced with the new ones on or before 31 May 2007. The central bank also stated that the ½ to 25 kobo coins withdrew withdrawn from circulation with from 28 February 2007.