I do think that Lincoln's mouth is open, but I believe it may be from die deterioration. The entire right side of Lincoln's face appears to have some deterioration. Or is this a minor variety listed somewhere? What's interesting is that NGC's page for this coin doesn't show varieties, but it says that a couple DDOs exist in the coin's description / summary. Maybe it could possibly be a unique die (?). Thanks in advance!
Why would his mouth be open? What you're seeing is almost certainly the result of overpolishing. The area around the eye appears somewhat flattened and also suggests as much.
