Chinese archeologists recently unearthed 48 tons of iron coins dating back 900 years in the northern province of Hebei
Experts hailed the find as a breakthrough because they had never before discovered iron coins in north China. Before this, historians believed that iron coins were only used south of the Yangtze River, where commerce flourished.
The coins, made during the North Song Dynasty (10th-12th century), were found in Cangzhou city by a local tourism department. Also at the site were some molds and stoves that suggest the existence of a mint.
Experts say the discovery will re-write China's history of coin production.