The 1925 Saint Gaudens gold piece on the left is an example of a graded, certified coin. As you can see, the coin has been graded by one of the top grading companies, PCGS. This coin was graded as an MS66, with the highest grade possible being an MS70. After the coin is assigned a consensus grade it is carefully placed into a durable, hard plastic, sonically sealed, tamper-proof holder to preserve the quality of the coin.

The grade defines the value of the coin. Each grading service guarantees the grade and authenticity of the coin. Slabbed and certified coins typically sell for much more than raw coins as seen below.

This 1935 Peace Dollar is an example of a raw coin. As you can see the coin is not "slabbed" and is not in a durable, hard plastic, sonically sealed, tamper proof holder. The quality of the coin is not preserved thus needs to be examined before it can be purchased. Do not confuse regular raw coins with bullion coins.

Raw coins typically sell much for much less than their slabbed counterparts. This Peace Dollar featured on the left was independently graded as an MS64, but because it has not been graded and slabbed it will not sell for as much as it could.