A Coin That Crossed Civilizations
In 621 CE, the Tang court issued a new bronze coin inscribed with four characters: 開元通寶. The name means roughly "currency of the inaugural era." Over the next three centuries, this coin became perhaps the most widely circulated object in East Asian history, found in hoards from the Sogdian oases of Central Asia to the rice paddies of Java.
The 開元通寶 also shows how the same written inscription could circulate across communities that assigned it different local readings.
- Chinese (Mandarin): kāiyuán tōngbǎo — the modern standard reading; the Tang court itself said something closer to khoj ngjwon thuwng pawX (Baxter's Middle Chinese notation, where a final -X marks the rising tone)
- Japanese: kaigen tsūhō — a Sino-Japanese reading that is mostly 漢音, though 通 tsū is not the Kan-on tō (dictionaries file it as 呉音 or 慣用音); it settled during the Nara period, when Japan modeled its coinage on Tang prototypes
- Korean: gaewon tongbo — the Sino-Korean reading, still used in numismatic literature today
- Vietnamese: khai nguyên thông bảo — the Sino-Vietnamese reading, preserving features of late-Tang (8th–9th century) Chinese phonology that Mandarin later lost
The divergence is most audible in the second character, 元. In Mandarin it is yuán; in Japanese gen; in Vietnamese nguyên—the Vietnamese form is actually closer to the original Tang pronunciation, because Sino-Vietnamese readings were borrowed earlier and frozen while Mandarin continued to change.
Coins excavated at Nara's Tōdai-ji, at Oc Eo in the Mekong Delta, and along the Silk Road at Dunhuang all bear the same inscription. The characters were the passport; the pronunciation was the local accent.