The one-yen coin is the oldest modern denomination coin design, it has remained the same since its introduction in 1955. This coin has been in constant production every year since its initial minting except for a brief halt in 1968 due to over production. The 1 yen coin is made of aluminium and weighs only 1 gram and will float on the surface of water. Mintage for 1974 was 1,470,000.