50 Yuan First chain pumps used to draw water

Part of China's long-running "Inventions and Discoveries of Ancient China" gold series, this issue commemorates the chain pump — a continuous loop of paddles or discs running through a wooden trough — which Chinese farmers were using to lift irrigation water as early as the 1st century AD. The device allowed controlled water transfer against gravity at a scale that transformed lowland rice cultivation across the Yangtze delta and beyond.

The series, issued through the 1990s in both gold and silver, was aimed squarely at the international collector market rather than domestic circulation.