How to Identify the Vietnamese Gia Long Thong Bao (cash coin)

What It Is

Gia Long Thong Bao coins were cast during the reign of Emperor Gia Long (1802-1820), who unified Vietnam and founded the Nguyen Dynasty after centuries of division. As the opening cash coinage of a new dynasty, these pieces are historically significant and follow the same cast, holed-cash format used across East Asia for well over a thousand years before and after.

Obverse Design & Inscription

The obverse shows four Han characters around the central square hole, read top, bottom, right, left: the reign name "Gia Long" followed by "Thong Bao," meaning "circulating currency." The script is generally a clear regular or semi-formal style, with somewhat thicker, bolder strokes than seen on later Nguyen issues.

Reverse Design

The reverse of standard Gia Long cash coins is typically plain, showing only the raised outer and inner rims framing the square hole. This unadorned reverse is consistent with everyday, low-denomination circulating cash of the period rather than commemorative or high-value pieces.

Size, Weight & Metal

These are small coins, usually around 22-24mm in diameter and roughly 3-4 grams, cast primarily in bronze or brass. Casting quality from the early Nguyen period is generally considered good relative to later, more debased issues from the dynasty's later years, though variation exists between mint batches.

Mint Marks & Where to Find Them

As with other Vietnamese cash coins, there is no separate mint-mark character in the way Chinese Qing cash coins often carry one; instead, collectors distinguish casting variants by subtle differences in character style, stroke thickness, and rim proportions. These differences correspond to different regional foundries operating under central authority.

Telling It Apart from Similar Coins

The key identifier is always the reign name in the top and bottom characters. "Gia Long" must not be confused with "Minh Mang," "Thieu Tri," "Tu Duc," or other Nguyen reign titles that share the identical coin format. It is also worth distinguishing Vietnamese pieces from contemporaneous Chinese Qing Jiaqing-era cash coins (1796-1820), which overlap in date but carry different reign characters and often a Manchu-script mint mark on the reverse that Vietnamese coins lack.

Judging Condition at a Glance

Well-preserved Gia Long coins show sharp, legible strokes on all four characters and a clean, unworn rim. Circulated examples show progressive flattening of the highest points of the characters and a smoothed, rounded rim edge. Since these coins are now more than two centuries old, moderate wear and surface oxidation are expected and normal rather than a defect.

Authenticity Red Flags

Be cautious of coins with an unnaturally uniform, bright surface, overly crisp modern-looking lettering, or a suspiciously light weight for their diameter — these traits often point to cast tourist reproductions rather than genuine period pieces. Genuine bronze cash coins usually show natural, uneven patina, some porosity, and casting irregularities consistent with hand-poured molten metal rather than machine-perfect uniformity.