Kai Yuan Tong Bao

The coin pictured is a Kai Yuan Tong Bao, the standard bronze cash coin of China's Tang dynasty and one of the most influential coin types in East Asian history. It is a round coin with a central square hole, the classic form of Chinese cast coinage that endured for two thousand years. The four characters around the hole read Kai Yuan Tong Bao (開元通寶), rendered here in the crisp seal-influenced regular script attributed to the calligrapher Ouyang Xun.

The name is usually understood as "inaugural currency" or "circulating treasure of the new beginning," marking a break from earlier coins that were named for their weight. On this example the obverse carries the four-character legend and the reverse is blank apart from the square hole, which is typical of the earliest Tang issues; later castings sometimes added crescents, dots, or mint characters on the back.

Because the type was cast in enormous quantities across nearly three centuries and imitated long afterward, individual pieces like this one are common and are collected as accessible, historically rich examples of medieval Chinese money rather than for any precious-metal content.

The Kai Yuan Tong Bao was introduced in 621 AD, early in the reign of Emperor Gaozu, the founder of the Tang dynasty. It replaced the older wu zhu coinage that had circulated in various forms since the Han dynasty, and it deliberately abandoned weight-based coin names in favor of an auspicious reign-style legend. The reform set the standard weight and module for the Chinese cash coin, and the tong bao ("circulating treasure") formula it established was copied by Chinese dynasties for the next thousand years.

Minted continuously through most of the Tang period, the type was produced at numerous imperial mints and in vast numbers, which is why so many survive today. Its influence spread well beyond China: cash coins of the same round-with-square-hole form and comparable legends were later cast in Japan, Korea, and Vietnam, making the Kai Yuan a foundational design for the wider East Asian monetary world.

Because the coin was cast rather than struck, and because it was produced over such a long span, there is considerable variety in calligraphy, size, and reverse markings. Later imitations and continued casting after the Tang mean that the type is often encountered outside a strictly datable context, and precise attribution of a given specimen usually rests on style and reverse details.

Identify the coin first by its form: a round bronze disc with a central square hole, cast rather than struck. The obverse bears exactly four Chinese characters arranged around the hole, read top-bottom-right-left as Kai Yuan Tong Bao (開元通寶). The lettering is in a distinctive early-Tang script with strong, even strokes; recognizing this four-character legend is the single most reliable identifier.

On the example shown the reverse is blank except for the square hole and a plain raised rim, which is consistent with the earlier Tang issues. Many later Kai Yuan castings show reverse features such as a crescent ("fingernail") mark, a dot, or a single mint character; the presence or absence of these helps place a specimen within the long production history but does not change the basic identification.

Typical pieces are modest in size and made of a bronze (copper-alloy) casting with a brown or greenish patina from age. Note that because the type was cast for centuries and widely imitated, reading the exact characters and comparing the calligraphy and reverse against reference charts is more dependable than judging by size or wear alone.

The Kai Yuan Tong Bao was produced in enormous quantities and is one of the most common of all ancient Chinese coins, so ordinary circulated examples sit at the affordable end of the market. Well-worn pieces with a plain blank reverse are typically inexpensive and are often sold in groups, making the type a popular entry point for collectors of Chinese cash.

Value rises with condition, sharpness of the calligraphy, attractive patina, and scarcer reverse varieties. Coins with distinctive reverse crescents, dots, or mint marks, unusually large or fine castings, and clearly early strikes can command more, while damaged, corroded, or heavily cleaned pieces are worth less.

Because casting spanned centuries and imitations abound, treat any single price as a broad guide rather than a fixed figure. For better examples, compare against recent sales of the same variety and, where value warrants, seek specialist attribution to distinguish early Tang issues from later castings and copies.