The coin has the look of a die-cap strike, but with the full rim on the reverse side it is more likely the result of a heavily clogged die, I.e., struck through "grease".
The odd toning on the obverse side does give some concern as to whether it is an authentic error. It appears to have been toned and cleaned and retoned/corroded - like coins that have been messed with after leaving the mint. Possibly it is an authentic error that saw some time in non-ideal storage, then cleaned.