The longer the age of ancient coins, the more impurities such as tin and lead are lost, and the duller the sound becomes. On the contrary, the closer you get, the clearer your voice becomes.
Method for observe copper color:
Generally, the materials of ancient coins are bronze, copper, brass and copper. Copper coins are easy to break, copper coins are not easy to break and wear. White copper is mostly used as sample currency. Before the Ming Dynasty, most coins were made of bronze, but there were no brass coins. If you find brass coins before the Ming Dynasty, you should be more careful.
Boiling water method:
Red-green rust or black rust handed down from ancient times often adheres to ancient coins. The rust of real money is formed by natural oxidation for a long time and has strong adhesion. Therefore, coins with suspicious rust color can be scalded with boiling water for 30 to 40 minutes. Rust is fake, and the rust of real money is not easy to get rid of.
Steel needle test method:
The rust of ancient coins is hard. Press the sewing needle vertically downward, and the needle will fall off as soon as you let go. The rust of fake products is often smeared with real rust mixed adhesive, which has certain elasticity and makes the steel needle not easy to fall off.
Style determination method:
The coins of each dynasty have their own style characteristics, such as knives and cloth coins in the Spring and Autumn Period and the Warring States Period, which are mostly cast by craftsmen at will, and the words Gu Zhuo are beautiful and simple; During the Western Jin Dynasty and the Southern and Northern Dynasties, Indian Buddhist documents were introduced into China, and the art of calligraphy was initially formed under its influence. The coin characters in this period are slender, flexible, charming and lovely, wonderful and exquisite. Tang, Song and calligraphy are closely combined, and most of them are made by celebrities, giving people a dignified, steady, graceful and lovely feeling as a whole; The currency of Liao Dynasty was loose in Qian Wen, but tight in Xixia and Qian Wen. The main characteristics of money in Ming Dynasty are square and blunt. These coins show the style of the times, which can be imitated by post-imitators, but it is not easy to convey their spirit, which provides an important basis for our identification.
Comparative version method:
The early ancient coins in China were all hand-cast, and even the mother money used for casting money was hand-carved, so there will be some differences between coins. If you find a batch of coins, their versions are exactly the same, and even some defects are not bad at all, you should suspect that there is a possibility of counterfeiting.
Component analysis method:
In order to improve the credibility of the auction, some auction houses often use some modern instruments to analyze the precious ancient coins collected before the auction. Commonly used methods include spectroscopy for chemical analysis, metallographic analysis, chemical capacity analysis and electronic nondestructive surface scanning determination. The above analysis data can be compared and analyzed by computer, which can give a more accurate answer. This method has high accuracy and reliability in qualitative and quantitative analysis of metal components of ancient coins.
Ultrasonic flaw detection method: