Clash Mark ?

Yup, and over the past few years they have become increasingly common.

First of all, there never was inspection of the individual coins after they were struck. The only inspection was of the dies before they were placed into use, and clash marks happen after that.

Second, these clash marks are the result of reduced depth in the design. 10 years ago these clash marks would have been impossible because the neck wasn't so low in relief. Back then and prior to then the clash marks always showed up first on the fields, and were easy to remove. Removing a clash mark like the one in this thread would involve polishing away the neck, which is impractical. They have been allowed as an acceptable flaw in the design and minting process and are not considered errors by the mint. Even if they were discovered (and they might have been), the mint would not remove the coins.

Lastly, these are not die varieties nor are they errors. The mint never purposefully 'made' die varieties. They happened because of the natural flaws in the process and lack of attention to detail by mint employees. An understanding of the process and the sheer number of dies used is necessary to understand why the die varieties that have slipped through did. Thousands of dies and billions of coins, it's understandable that not all of them are going to come out perfect.

puff = picture. Who says you can't teach an old old dog new tricks. Thanks Metalman