How We Authenticate Coins — Tooling and Size

Vietnamese coins were produced in many parts of the country, at different times, and under varying economic conditions. At many times in Vietnamese history, there were copper shortages. Compared to Chinese coins (and modern replicas), they vary much more in size, thickness, and shape. Like Chinese coins, Vietnamese coins were made by casting bronze -- modern fakes are made from die-stamped metal. The difference in tooling marks is clearly visible between these two production methods!

Real coins have ridges and imperfections that vary between coins. The space between the characters often has a 'sandy' surface texture if the coin is completely cleaned.

Fake coins are perfectly round, have little or no variation between coins of the same type, and are all the same size. In short, they look like a modern, mass-produced item rather than something imperfect made at scale in ancient times. The die-stamping process also results in perfectly smooth surfaces.

In the image above, all the coins are genuine. The coins in the bottom row have been cleaned very aggressively. Besides being very difficult to do, this makes the coins look boring -- what's the point of sourcing genuine coins, then erasing the history they've accumulated? We've done it anyway for the three bottom coins so you can more clearly see the tooling marks, and variations between coins. Normally the patina and clay make these somewhat harder to see.