Distinctions Between Almost Uncirculated (Au) And Uncirculated

Great question, so I will explain only how I learned the difference which may help. The most misunderstood aspect of coin grading is how the grading scale works. Think of it like having three different "buckets." or "groups". The first bucket/group is only for circulated coins, the second bucket/group is for About Uncirculated (AU) coins, and the third bucket/group is for Uncirculated (Mint State, or MS) coins.

Circulated coins have the widest scale for grading. These range from P-1 through EF-49 grades. P-1, or poor, is the lowest grade a coin can be graded. This is a coin that is just barely recognizable even though it has heavy wear and most of the detail has been worn away. At the upper end of the scale, this would be a circulated coin that has slight wear on the highest points of the coin. This keeps it out of the About Uncirculated category.

The AU portion of the scale starts at 50 and runs through 59. The AU-50 coin might never have circulated in commerce, but because it has scuff marks, has been through several coin-counting machines, and has been handled a small amount, it is no longer in Mint State. So we put it in the AU bucket and give it the bottom grade of AU-50 if it's ugly and AU-58 if it's not. This is oversimplifying a little, but it demystifies why the grading scale seems to go from "appealing coins" to "ugly coins" and then back to "appealing."

The MS scale (from MS-60 to MS-70) isn't just a continuation of the previous scale of AU coins. It is an entirely separate mini-scale of 11 grades that begins with the "basal state" MS-60 Uncirculated coin. This is an ugly, bag-marked, no-luster dog, but it is technically Uncirculated. Some of those scratches you mention on quarters can happen from contact with other coins in sealed mint sewn bags for example. By comparison, the AU-58 coin beneath it has attractive eye appeal and nearly full luster. The reason a coin that grades an AU-58 is because it looks much nicer than a coin that grades MS-60. Additionally, they are actually in separate "buckets"/groups of the grading scale. The coin that grades EF-40 has lost only about 5% to 10% of its detail, but the coin that grades F-20 has lost about 60%

The grading scale should technically be the same across the board for all three, but there are minor differences in how the grades are given on labels. There are also differences in regards to value based on grade given - a PCGS graded coin may sell for more than an ANACS graded coin at the same grade for example, but may have cost more to grade due to the membership and grading fees. Every series has its telltale spots for identifying wear: the headband on the Indian Head cent, Lincoln's hair, the horn on the Buffalo nickel, and so on. There are some books such as Making the Grade ( CoinWorld book), ANA Grading Standards (Official ANA Grading Standards for United States coins), and Grading coins by photographs 2nd edition that go into more details, as well as specialized books such as a guide book of Lincoln cents 3rd edition for example that might go into details of that series.

Fewer than 1% of the coins graded by NGC get a Star rating. The star is like a beauty pageant for coins, to decide if they have "exceptional eye appeal." The grade designation is not as important as how the coin looks compared to others in its grade. NGC admits that these evaluations can be subjective, but If any one of the quality-control graders objects to a Star designation, it's over. To be considered for a Star Rating, a coin must first meet certain quality standards. It must have a full vibrant luster and be free of any distracting irregularities, spots or blemishes. Coins submitted for stardom can be either "white" (untoned) or toned. Toned coins face even more hurdles. The toning must be considered attractive, with good contrast if there is more than one tone present. It also must have full luster unimpeded by the toning. And while the toning can be single or multicolored, it can't have any areas that are dark brown approaching black. https://www.ngccoin.com/news/article/806/

ultra cameo ngc, deep cameo PCGS In order to obtain a cameo designation, both sides of the coin must have cameo contrast. If one side of the coin has a "deep cameo" and the other side only has a "cameo," then the coin will receive a "cameo" designation. "Deep cameo" may also be referred to as "ultra cameo". Before 1971, proof coins made at the U.S. Mint were produced with dies that were chemically etched or sandblasted to impart a frosted finish on the devices. To give the fields a mirrored finish, the flat areas of the dies were polished to a mirror-smooth consistency. Unfortunately, a set of proof dies only produced about a hundred coins with cameo contrasting devices and mirrored fields. As the dies continued to be used, the devices that once had a frosted finish slowly eroded due to the friction of the striking process until the entire coin had a brilliant mirrored finish. Coins with a high degree of cameo contrast are especially prized by collectors of early-proof coins https://www.greysheet.com/news/stor...-proof-coins

PCGS defines full steps (FS) as "the designation following the numerical grade of some regular-strike MS60 or higher Jefferson nickels that have at least five separated steps (lines) at the base of Monticello," adding, "Any major disturbance or interruption of these steps or lines, whether caused by contact, planchet problems, or another source, will result in the coin's not being designated FS." NGC: What are 5FS and 6FS? https://www.ngccoin.com/news/articl...eps-nickels/

NGC: Full Bands and Full Torch dimes. Dimes do not need to be Mint State to qualify for the FT and FB designations, but it should be no surprise that most that qualify are Mint State. These designations are not used for Proof dimes, which are assumed to have been well-struck. https://www.ngccoin.com/news/articl...ading-dimes/

The CAC green sticker also adds to the value and demand. Certified coins of the same grade can be of varying quality. Many of today's collectors want coins that are solid or premium quality for their assigned grade and CAC will verify previously graded coins to be a solid/high quality example for that grade. There are many coins that are certified accurately for their grade. Unfortunately, it is an inescapable reality that many are at the lower end of the quality range for the assigned grade. CAC's rejection of a coin does not necessarily mean that CAC believes the coin has been over-graded. It simply means that there are other coins with CAC stickers that are of higher quality for the grade. CAC will eventually reject tens of thousands of accurately graded coins.