Whether it is ancient coins or modern and current issued coins and commemorative coins, for coin collectors or coin dealers, the most important coin collection and sale is only two key points, the true and false coin and its value. However, these two determinations are by no means the sole one of the seller or the buyer. Most sellers in the general market will claim that the coins they sell are guaranteed to be genuine and can be exchanged as fake bags. The problem is that if the buyer unilaterally considers it to be counterfeit currency, the seller may also find it difficult to identify, and the dispute will arise. Therefore, between the buyer and seller must have a professional third party to give recognition and public judgment? At present, the arbiter is the Coin Laboratory. The function of the coin laboratory is like an insurance company, after the identification gives the true money of the guarantee and the grade to assess the value of the coin. As long as it is the coin has identified by the coin identification, if found to have been misidentified, the buyer or seller can claim compensation from the coin laboratory. Therefore, the buyer and seller will not create an unresolved dispute. At present, the coin identification method is as follows: 1. it is called the weight of the coin. Generally counterfeit coins are lighter than real coins, but some lead-clamped counterfeit coins are heavier than real coins. Although the surface is slightly worn after the use of the real coin, it is very different from the standard weight of the original coin. 2. Listen: it is to use hard objects to knock on coins, judging by the sound it makes, because the sound of various metals is different. Making a sound in silver is definitely different from the counterfeit coin made of copper lead. 3. Look: use the eyes or with the help of a magnifying glass to look at the coin layout of the pattern text and luster. Pseudo-pattern is how rough and delicate, the graphic text is blurred, the money body text is not standardized, but also uneven like puffy. The edges of coins are most prone to wear and tear or crack. However, according to the above three methods may still not be 100 percent guaranteed the authenticity of the money. Because the material composition of the coin is metal, a particular metal or alloy has its fixed weight and density, which cannot be forged. Even if the weight of counterfeit coins is the same as that of real coins, the specific gravity and density of the counterfeit currency are different because of their different metal composition. If the dimensions are the same, the weight must also be different. This study is to the proportion of real coins as the standard, after test by stereometry, so that the collection of coins more than one piece of protection.