N Grade coins are unique to the PCGS grading system and are so designated with a coin is not graded.  Beginning in 2013 PCGS added a general indication of how the coin would have graded had it not been disqualified.

A coin given a designation of N-94 has been altered through the application of a substance.  This No Grade covers anything added to the surface of the coin to either "improve" its appearance or to cover marks.

Surface alteration methods include adding: dental wax, putty, lacquer, nose grease, etc. "Thumbing" is the application of a putty-like material to fill in marks, scratches, and other defects or to haze over portions of the coin. Coatings (such as lacquer), while intended to protect coins, result in a No Grade because it is impossible to determine the quality of the underlying surfaces.