Your picture quality is really very good.
The O shows
Die Deterioration Doubling. The adjacent N actually shows it better. Over extended use, the face of the die begins to experience cold metal flow from striking hard metal coins. That is particularly true of nickels and clad coins, which have a 75% copper, 25% nickel composition. Nickel was used in WWII to harden steel tank armor. Anyway, the die face will slowly deform towards the rim of the coin and also towards any large cavities on the die. In the case of a
Jefferson nickel reverse, that happens to be the Monticello building, which is a huge cavity in the die. The tops of the coin letters stay where they are as those are the bottom of the die pits, below where the surface metal is moving.