A 200 year old cast forgery
Khai Thái Nguyên Bảo, 開泰元寶
Old forgeries are sometimes difficult to spot because they may have natural wear, scratches, oxidation, and some-times real patina. The only way to determine if such a coin is a forgery is to study the coin's workmanship and calligraphy. The Khai Thái Nguyên Bảo pictured on the right is an old forgery, which has acquired natural wear, scratches, and oxidation. Many such forgeries were made over a hundred years ago to satisfy a demand for such coins in Japan.
The coin's calligraphy is suspicious and different from any recorded variety in the Vietnamese numismatic literature. When compared to the common Tang dynasty Kai Yuan Tong Bao on the right, the Khai and Bảo characters are strikingly similar. The position and overall balance of the four characters on the forgery are not good, and the calligraphy on the left side of the coin is denser than on the right.
The coin was made by altering the right and bottom characters of a Kai Yuan Tong Bao and then using the altered coin to cast the forgery. Further evidence of the workmanship can be seen in the field regions on the top and bottom of the coin. The field on the top of the forgery has a bumpy texture that comes from the Kai Yuan's original surface, probably from patina present on the surface at the time the forgery was cast. The bottom field does not have this same bumpy appearance and is deeper. Both are signs of the forger's workmanship.
Another sign of the forgery is the size of the coin. Kai Yuan coins come in many sizes but ones produced during the height of the Tang dynasty are common and fairly uniform in size. The coin on the right is an example of this common type of Kai Yuan and is probably similar to the one used to produce the forgery. The recast coin on the left should therefore be about 5% smaller than the coin on the right, which it is.
Although old forgeries are often difficult to spot, they sometimes have certain distinguishing features. The most common is a smooth surface with dark oxidation rather than the usual crusty surface with colored patina. This is because such forgeries were in collector's hands from the time they were made and were never buried in the ground. New forgeries will often have artificial red or green patina.
Some real coins can have the same smooth dark brown appearance, particularly old Chinese and Vietnamese coins found in Indonesia. Many of these were kept as charms or were never buried. Rare coins that have been in collectors' hands for a very long time can sometimes have a similar appearance.