NGC will add two English letters before the digital grade of coins to indicate the production mode and overall appearance of coins. Among them, MS is widely used, and MS stands for coinage country, and such coins are minted and circulated. PF stands for evidence. These coins were specially minted for collectors. Another casting type is SP, which stands for specimen. The coins described in this state can not meet the standard of refined coins, but their state is better than that of ordinary currency. Ms. Mint's status. Coin casting remains the same as when it was issued, with a rating of 60-70. PF proves that coins are specially used for collection.

1. The bond rating standards of rating agencies can be divided into AAA, AA, A, BBB, BB, B, CCC, CC, C and D from high to low. The first four bonds are "investment-grade bonds" with high credibility and low risk; The bonds at the beginning of the fifth level have a low reputation and are "speculative bonds".

2.NGC uses the internationally recognized Sheldon 1-70 numerical rating standard, which was first used in the United States in the late 1960s. When NGC started its business in 1987, it adopted this rating method which was recognized as the industry standard. The following is the numerical grading standard of NGC, as well as the main casting types and nomenclature. Coins with defective appearance cannot be rated by NGC value, and NGC detail rating can be accepted as appropriate.

3. There are ten grades. The main reason of bond credit rating is to facilitate investors to make bond investment decisions. Investors have to bear certain risks when buying bonds. If the issuer fails to repay the principal and interest at maturity, investors will suffer losses, which is called credit risk. The credit risk of bonds varies with the repayment ability after issuance.

4. It is very important for investors, especially small and medium investors, to know the credit rating of bonds in advance. Due to the limitation of time, knowledge and information, it is impossible to analyze and select many bonds. Therefore, it is necessary for professional institutions to objectively, fairly and authoritatively evaluate the debt repayment reliability of the bonds to be issued, that is, to carry out bond credit rating, so as to facilitate investors' decision-making. Bond credit rating is mostly corporate bond credit rating, which evaluates the reliability of repayment of principal and interest on schedule for specific bonds issued by enterprises with independent legal personality, and marks its credit rating. This credit rating is to provide information services for investors to buy bonds and the circulation and transfer of bonds in the securities market.

5. The face value of the bond refers to the face value of the bond, which is the principal amount that the issuer should repay to the bondholders after the bond expires, and it is also the calculation basis for the enterprise to pay interest to the bondholders on schedule. The face value of bonds is not necessarily the same as the actual issue price of bonds. If the issue price is greater than the face value, it is called premium issue; If it is lower than the face value, it is called discount; And if it is equivalent, it is called parity issue.