It's a weird one - I remember when I was searching through bank bags as a schoolkid in the late 60s; now and again I'd see 1915 or 1916 pennies where the head just 'looked weird', especially around the ear. I didn't think anything of it at the time, but I did notice each one when it appeared. It may be that the difference is more obvious on a more worn penny than on one that's EF or better? In other words, the ear is less worn than it should be and seems a bit more sunk than on normal examples.