George Marino mastered the original release of Metallica's 1991 album Metallica, known as The Black Album.
Mastering is the final major audio stage before a record is manufactured or distributed. It balances the completed mixes, establishes a consistent overall sound, and prepares the album for its original release formats. Marino received that mastering credit on the 1991 edition.
The album's production credits also distinguish several other technical roles. Bob Rock, James Hetfield, and Lars Ulrich were associated with production; Randy Staub handled engineering; and Mike Tacci assisted with engineering. Mixing was credited to Rock and Mike Fraser.
Later editions have separate restoration or remastering credits. Bob Ludwig is credited with the 2021 remaster, so his name belongs to the anniversary-era version rather than the original 1991 mastering credit. That distinction explains why both engineers are associated with different editions.