The Numismatic Guaranty Company (NGC) is a leading third-party service for authenticating, grading, and encapsulating coins on a 1-to-70 numeric scale called the Sheldon scale. The process involves submitting coins, which are then evaluated by professional graders, sealed in secure holders, and backed by the NGC Guarantee. 

The NGC grading scale

NGC primarily uses the 70-point Sheldon scale to evaluate the condition of a coin. Grades 1 through 59 describe circulated coins, while 60 through 70 are reserved for uncirculated (mint state) coins. 

Circulated grades (1–59): 

• PO (1) to AG (3): The lowest grades, with only enough detail to identify the coin's date and type.
• G (4–6) to VG (8–10): Heavily worn coins where major design elements are visible, but flat.
• F (12–15) to VF (20–35): Coins with moderate to light wear on the highest points of the design.
• XF (40–45): Worn on the high points, but much of the design is still well-defined.
• AU (50–58): Shows only a trace of wear on the highest points, with some original mint luster still present. 

Uncirculated grades (60–70): 

• MS-60 to MS-70: Mint State coins that show no wear from circulation. The grade is based on a combination of factors, including strike, luster, and the number and location of contact marks.
• MS-70: A coin with no post-production imperfections visible at 5x magnification. 

Other common designations:

• PF or PR (Proof): A coin struck in a special format for collectors. These also receive a 1–70 grade.
• SP (Specimen): A designation for coins that fall between a typical business strike and a proof.
• Plus (+) and Star (⭐) Designations: A coin that is at the high end of its assigned numeric grade receives a "+." A "⭐" is given to coins with exceptional eye appeal. 

NGCX 10-point scale:
In 2023, NGC introduced an optional 10-point scale called NGCX for modern coins (minted after 1982). A grade of 10 on this scale is equivalent to a 70 on the Sheldon scale. 

The NGC grading process

1. Become a member: Direct submissions to NGC must be made through a paid Collectors Society membership or through an NGC Authorized Dealer.
2. Submit coins: Select the appropriate grading tier based on the coin's value and desired turnaround time. After filling out the submission forms, prepare your coins by placing them in non-PVC flips.
3. Authentication and grading: At least two professional numismatists examine each coin. To ensure impartiality, graders do not know the submitter's identity and cannot commercially buy or sell coins. NGC also grades error coins and ancient coins.
4. Details grading: Coins with surface problems like cleaning, scratches, or damage are not assigned a numerical grade. Instead, they receive a "Details" grade (e.g., "VF Details—Cleaned").
5. Encapsulation: After grading, authentic coins are sealed in an NGC tamper-evident holder, or "slab." The label includes the coin's details, grade, and a unique certification number.
6. Verification: The certification number can be used on the NGC website to view the coin's details and photos. 

Why get coins graded by NGC?

• Authentication: NGC provides independent, third-party authentication to protect against counterfeit coins.
• Increased value and liquidity: Graded coins are more trusted and often command a higher price in the market. The population report, which tracks the number of graded coins at each level, can reveal scarcity and increase a coin's value.
• Preservation: The archival-safe, sealed holder protects the coin from environmental damage.
• Market confidence: The standardized, objective grading system establishes a uniform level of quality that reduces disputes over a coin's condition. 

*All info is from their website this is for quick reference