What your coin's grade actually means
How the Sheldon scale works, why two coins that look identical can grade differently, and when third-party grading is worth paying for.
Grading is the single largest factor in what a collectable coin is worth, and it is the part most people arrive knowing least about.
The Sheldon scale
Coins are graded on a 70-point scale. The numbers are not evenly spaced in terms of value — the difference between two adjacent grades near the top of the scale can be enormous, while several grades near the bottom may be worth much the same.
Broadly, circulated coins run from Poor through Good, Fine, Very Fine and Extremely Fine to About Uncirculated. Coins that never entered circulation are Mint State, from MS-60 to MS-70.
Why two identical-looking coins grade differently
Wear is only one input. Strike quality, lustre, contact marks, toning and eye appeal all move a grade, and several of those are difficult to see without practice and good light.
This is why we do not grade across a counter in front of a queue. It takes time and it takes handling the coin.
When third-party grading is worth it
Sending a coin to PCGS or NGC costs money and takes weeks. It is worth it when the coin is valuable enough that the grade materially changes what it will sell for, and when you intend to sell into a market that expects certification.
For most material, it is not worth it. We will tell you honestly which category something falls into.
What not to do
Do not clean a coin. Not with polish, not with a cloth, not with anything. Cleaning leaves marks that graders recognize immediately, and a cleaned coin is worth a fraction of the same coin left alone. This is irreversible and it is the most common way people destroy value before they ever reach us.