1952 British West African sixpence
The dissolution of British West Africa began in the 1950s and as a result, the coin mintages were either reduced or non-existent in many years. In the case of the 1952 sixpence, the mintage was reduced - 2,544,000 1952 sixpences were struck, down from 6,120,000 in 1947 and 4,000,000 in 1945 and 1946. In spite of the moderate mintage, the reduced demand seen by the lack of production from 1948 to 1951 continued, with almost the entire 1952 mintage being melted (Linhoss, https://coinbooks.org/esylum_v16n35a19.html).
The coins were reportedly melted down at the Riverside Metal Company in New Jersey with just 167 coins being retained (Linhoss, https://coinbooks.org/esylum_v16n35a19.html), probably illegally. It is unclear when the coins first appeared on the market.