DWLange

It has a touch of strike doubling, but no die doubling.

There are no high relief pieces in the state quarter series.

Moore's letter could be the reason that the Classic Head gold coins, initiated during his administration, lacked a cap on Liberty's portrait.

It appears that the dies were slightly mis-aligned, with the rim thus wider at one side than at the other. The error is too slight to carry a premium, but that's a good observation on your part.

It is a proof. That's a nice find.

The same date punch was used for each coin. Its position varies routinely, due to hand punching with the use of a jig. The apparent size varies with the depth to which the numerals were punched initially and with how much the die was polished subsequently. A repolishing of the die can diminish the size of the numerals and make them seem to be further apart.

The mintmark and ribbon end show strike doubling.

My original ANA membership number is just five digits, and I have it engraved on a silver membership medal that the ANA no longer offers. When they discontinued these medals about 20 years ago I bought half a dozen remainders with their boxes, and when silver went up around 2010 I sold them on eBay for quite a profit. The ANA's numbering system with prefix numerals has baffled me for years, but I suppose it's necessary for computer processing. I haven't checked recently to see whether my life membership number has been retrofitted with additional numerals.

Until the Nazis adopted that symbol in the 1920s it was seen in many places within the United States as a symbol of good luck and prosperity. It still may be seen on some buildings pre-dating that time.

That centennial is coming up in 1924. I believe just two of the four airplanes made it all the way around the world, but it was still an amazing achievement with so few aviation facilities at the time.

The 1972-D half meets NGC's criteria for a "NO FG" designation, but this is not rare and adds little value. It's more of a personal choice as to having it graded and attributed.

It has some strike doubling, which is common on S-Mint cents 1968-73. It's not a variety and adds no value.

Silver eagles are struck at several mints without mintmarks, so they're typically not distinguished as to their origin. The one identified as P came from a box bearing a seal of the Philadelphia Mint and was so certified.

I agree that my figure was a bit conservative, because I didn't want to seem too negative about a popular issue.

It also gave them that smoky scent...

A thousand or so 1856 Eagle Cents are not that many, given the popularity of collecting small cents. Comparing it to the 1909-S VDB cent (probably 15,000+ survivors) is not that meaningful in my opinion.

When exposed to chemical contaminants the copper core of clad coins will erode more rapidly than the more durable copper-nickel outer layers, leaving a sunken center. It's just environmental damage.

It appears to be simply damage to the coin. There is no economic incentive to alter the mintmark on dollars dated 1900, as there are no keys for that date.

As someone who bought and graded coins for almost 20 years before there were slabs I found the grading standards presented in PG to be on the loose side by about half an alpha grade. In other words its Fine was equal to VG-F as compared to my own grading and that of the dealers whose grading I and others respected. Regarding the task of assembling a photographic grading guide, I was faced with that chore fir the three books I wrote as part of the "Complete Guide to" series. I found that few circulated coins ever matched the ideal standards I wanted to depict. Dozens of coins were photographed, and in many instances the obverse and reverse images were paired from two different coins to achieve that ideal..

This is the typical look of a coin that was found with a metal detector. It was probably all reddish-brown when retrieved, but the encrustation has partially worn off of the higher points.

There are several lesser DDO varieties for 1972, but your coin is not one of them. They are listed and displayed here: https://www.ngccoin.com/variety-plus/united-states/cents/lincoln-cents-memorial-reverse-1959-2008/?page=1

Closer to home and easier to use: https://www.ngccoin.com/variety-plus/united-states/cents/coronet-head-cents-1816-1839/?page=1

And then again in 2018 with the Innovation Dollar series, though no one has made any pretense of these being circulating coins. So much for "innovation"...

The $25 Templeton Reid piece was unique and has not been seen since. Since it looked nothing like a federal coin and thus could be neither spent nor deposited at a bank, the robbers are believed to have melted it.

Far more effective than just banning them from EBay...