Song Yuan Tong Bao

The most intriguing fact about the Song Yuan Tong Bao is that it was cast in such enormous quantities—estimates suggest billions during its era—that it effectively turned copper into the lifeblood of the Northern Song economy, funding everything from grand canals to endless border defenses.

Weighing around 3 to 4 grams and struck from copper alloys, these coins featured the standard square hole design, with the inscription indicating the reign of Emperor Shenzong, who issued them from 1074 onward. Variations in calligraphy and mint marks hint at production across multiple sites, though exact locations remain murky in historical records.

Counterfeiting was rampant, as one might expect with coins this common. I've lost count of the fakes I've examined over the years.