
The image is a blue plaque with white text written in Chinese characters. The text reads "In the Han Dynasty, Sannenxia was one of the leading iron-smelting centers nationwide. A special position of iron officials in charge of affairs con-cerning iron smelting was established. 4,000-odd kiln-stored iron wares dating back to the period between the Han dynasty and the Northern Dynasty. They were 60-odd shapes, bore inscriptions of over 30 kinds and came from dozens of workshops. Most importantly, they embraced almost all the fundamental structure of modern cast iron. Especially amazingly, nodular cast iron was also found there, which is a malleable cast iron of higher strength and certain toughness and a possible substitute for some cast steel. Nodular iron was already seen during the Warring States period on a gradual increase after the Western Han Dynasty. However, nuclear cast iron by modern industrial manufacture was only seen around 1948. The fact that nuclear castiron can be achieved without adding any nodulizing agent in China as early as 2,000 years ago."
