10 Yen - Shōwa 23mm pattern, plain edge

In the chaotic postwar years following Japan's surrender, the mint experimented with numerous pattern designs and compositions before settling on the bronze 10 yen that entered circulation in 1951. This nickel pattern at 23mm never advanced beyond trial stage, almost certainly a casualty of nickel's strategic designation as a controlled material under Allied occupation oversight — the same constraint that pushed Japanese coinage toward bronze and aluminum during this period.