The answer is that the average person can't. "MS" is a grade meaning "Mint State"; i.e. the coin is uncirculated and in the same condition as when it was minted. That grade is further broken down into 11 sub-grades ranging from MS-60, the lowest acceptable condition that can still be considered Mint State, all the way up to MS-70 for a coin that is in absolutely flawless condition.
To assign a specific grade within MS, an appraiser requires special training. They have to look for particular details on each type of coin and combine them to assign the numerical grade. Those items might be as specific as the sharpness of the lettering or how the hair on a portrait appears.
Normally the major numismatic societies employ a staff of professional graders. Even with their training decisions can still be subjective so it's sometimes necessary to have a coin evaluated by more than one agency.
Uncirculated, or Mint State, coins are graded from MS60 (typical uncirculated) to MS70 (perfect). A MS66 coin may have noticeable, but very minor defects, be well-struck, have above average luster and eye appeal.
The most expeditious way to get a coin graded is to locate a coin shop nearby - present the coin to the owner for grading. If he/she is uncomfortable to do so, he/she will refer you to a numismatist (experienced coin collector).
US coins are usually graded on the Sheldon scale. The Sheldon scale grades coins from 1-70. A coin graded 1 is very, very, poor and is basically only identifyable by the size of the coin. A coin graded 70 is perfect with no defects at all. Most coins grade somewhere in between the two extremes.
MS66 is a specific grade for a coin's condition on the Sheldon Scale, which grades coins on a scale of 1-70. MS stands for mint state, and a 66 out of 70 is nearly flawless.
To get that specific of a grade on a coin, it would need to be professionally graded though a service like PGCS, though a coin dealer in a shop could give an approximate grade.
Uncirculated, or Mint State, coins are graded from MS60 (typical uncirculated) to MS70 (perfect). A MS66 coin may have noticeable, but very minor defects, be well-struck, have above average luster and eye appeal.
In coin grading terminology "MS" stands for "mint state" or the state a coin is in when minted and uncirculated. Showing no signs of wear or indication of circulation. MS is interchangeable with "uncirculated". Although MS coins have no wear from circulation they may have varying imperfections from the minting process. To allow for that, the "MS" coins are graded on a scale beginning with 60 and going up to 70 (this is the highest number, which indicates supposed "perfection"). So MS66 would mean a "mint state" or uncirculated coin graded 66 out of a possible 70 on the grading scale. A very nice coin.
15 gold coins
In a case like this, it really helps to identify who graded the coin, if the coin came with a "certificate of authenticity" it raises red flags for a coin collector because it sounds like you bought the coin off of TV or by a shady dealer. If the coin was graded by a reputable dealer like PCGS or NCG, you might have a coin worth about $50 or so. If your coin was self-graded by the dealer or graded by a no-name grading company, you might only have a coin worth a bit more than melt because those tend to overgrade, and you might only have an AU coin, not a MS coin. Without knowing who graded it or seeing it in hand, it is hard to tell what exactly it is worth.
The most expeditious way to get a coin graded is to locate a coin shop nearby - present the coin to the owner for grading. If he/she is uncomfortable to do so, he/she will refer you to a numismatist (experienced coin collector).
SIMPLE ANSWER: Circulated coins are graded by how much wear the coin shows. Mint State coins are graded by how well the coin is stuck.
To set things straight and so that you can find your coin when doing searches, that's ST GAUDENS and NO MOTTO. Numismedia lists a retail fair market value of an MS66 no-motto St. Gaudens double eagle at roughly $3800 for a Philadelphia coin, and 10 times that for a Denver coin. In any case you need to be sure that your coin has been certified by one of the major grading services. MS66 is a stratospheric level for a coin and only a trained expert can assign that grade reliably.
A 1921 Philadelphia issue Morgan graded MS-66 has a average retail value of $800.00 but to get even close to this price, it must be slabbed by a known professional grading service.
US coins are usually graded on the Sheldon scale. The Sheldon scale grades coins from 1-70. A coin graded 1 is very, very, poor and is basically only identifyable by the size of the coin. A coin graded 70 is perfect with no defects at all. Most coins grade somewhere in between the two extremes.
The term "circulated" in the world of coins means not in mint condition. In particular, any coin that you find in change is by definition circulated. The way you can tell is by looking closely at the coin and checking for dents, scratches, wear and other signs that the coin has been used (circulated). If in doubt, get it graded by your local coin shop and have them evaluate it for you.
A slabbed coin is a coin that was graded by a grading service. There are many grading services out there. You can use google to find some of them. Having a coin graded can give you the exact value and therefore is easier to determine its value.
MS66 is a specific grade for a coin's condition on the Sheldon Scale, which grades coins on a scale of 1-70. MS stands for mint state, and a 66 out of 70 is nearly flawless.