In 1912 a West African Currency Board was established to arrange for the production and supply of coins (small denomination coins had already been issued starting 1907).
The first issue of silver, in the denominations 3 pence, 6 pence, shilling and 2 shillings, was struck at the Royal Mint, London in 1913, and made legal tender in Nigeria, Gold Coast, Sierra Leone and Gambia by a local Currency Act dated 26 June 1913.
1913 was also a year when a large crop of cocoa valued at almost 2 1/2 million pounds saw a great demand for silver coins. In addition to 889,000 pounds of West African silver (all the Royal Mint could strike) an additional 539,700 pounds of Imperial silver coin was needed. Such fluctuation in demand made the provision of a silver coinage very difficult.
During World War I 530,000 pound of silver coin was returned to Britain for sale as bullion to raise internationally accepted forms of money.
Interest in the production of a silver coinage led to the request for the provision of proof and specimen sets for official commemorative gifts. Sets containing two coins of each denomination were struck in proof quality while single coin sets were made out of selected uncirculated specimens.
References to additional information:
[Book] Remick, Jerome. 1971. The Guide Book and Catalogue of British Commonwealth Coins, pp 87-95.
[Book] Vice, David. 1983. The Coinage of British West Africa & St. Helena 1684 - 1958.