How to Identify the Korean Sangpyeong Tongbo Cash

What the Coin Is

The Sangpyeong Tongbo (常平通寶, "ever-normal circulating treasure") was the main cash coin of Korea's Joseon dynasty, first cast in the 1630s and produced in large quantities especially from the later 17th century into the late 19th century. It follows the traditional East Asian round coin with a square center hole.

Obverse Design & Inscription

The obverse reads clockwise 常平通寶. Character style varies by mint and period, but the four-character phrase itself remains constant throughout the coin's long production run, making it easy to identify at a glance.

Reverse Design & Mint Marks

The reverse is where individual issues are distinguished. Most examples carry one Chinese character above the hole identifying the casting bureau or mint, often abbreviating a government office or region, sometimes paired with a number or additional character below or beside the hole indicating a specific furnace or batch. This reverse marking system is the primary way collectors sort Sangpyeong Tongbo into hundreds of cataloged varieties.

Size, Weight, Metal, Edge

Standard pieces are cast in bronze/brass, typically around 25-27 mm in diameter, though larger denominations issued later in the 19th century during currency reforms were struck at increased size and weight to represent higher face values. Edges are plain and unmilled, consistent with cast cash coinage.

Telling It Apart from Similar Coins

Because the four-character inscription is unique to Korea, confusion mainly arises with generic cash-coin shapes from China or Japan. The inscription 常平通寶 does not appear on genuine Chinese or Japanese issues, so reading the obverse characters is the fastest way to confirm Korean origin. Within the series, reverse mint characters, rather than the obverse, distinguish one variety from another. It is also worth noting the character style itself: earlier casts tend toward a somewhat thicker, more angular brushwork, while later 19th-century pieces often show thinner, more standardized strokes as casting technique and central oversight of the mint bureaus evolved.

Judging Condition at a Glance

Look for clear, evenly cast characters on both sides and a full, undamaged rim. Because so many were produced, common varieties in worn condition are typical; sharper strikes with legible reverse mint marks are more desirable to variety collectors even when the coin itself is not rare. Pay attention as well to the squareness and centering of the central hole, since a crooked or off-center hole can indicate either careless period casting or a later, cruder reproduction.

Authenticity Red Flags

Modern tourist reproductions exist, often with unnaturally smooth or overly dark artificial patina, blurry or incorrect reverse characters, or a diameter and weight that doesn't match known genuine ranges. A reverse mint mark that doesn't correspond to any documented casting office is a sign of a fantasy or reproduction piece rather than a period coin.