The reason I think it is an over abraded (over polished) die, is the lack of detail in other areas of the face of Lincoln. The bridge of the nose, the cheeks, and other areas also lack detail. A thing that I do find odd, is that I can find no other examples, so far, of this on other 1977 D pennies. I should think that other examples of this should be available.
There were more than four billion of the '77D produced. There are probably others "floating" around (pun intended) in the marketplace. How many people do you think examine every coin they get in change? Chris
Yep, overpolished die, and this shows up on several if not many different years. There is nothing really special about them even though Coin World made a big deal over the discovery of "floating head" 2019 cents this year. Must have been a very slow news week.