1 Yen - Shōwa Aluminium pattern

In 1950, Japan's mint was still operating under Allied occupation authority, and the question of what the postwar 1 yen coin would look like — and what it would be made of — went through several unresolved rounds. This aluminium piece is a pattern from that process, never approved for circulation. The brass 1 yen had already been abandoned as impractical, and the occupation authorities were pushing for lighter, cheaper coinage as Japan's economy remained severely depressed.

The aluminium composition was ultimately adopted, but not until 1955. Five years separated this pattern from the coin Japan actually issued.