The Otricoli bust raises a question that copying always raises: what exactly is being preserved when nobody making the copy has ever seen the original? By the time a Roman sculptor carved the marble that would end up buried at Otricoli, Pheidias's chryselephantine Zeus at Olympia, built from gold and ivory over a wooden frame, was already centuries old and would eventually be lost entirely, reportedly destroyed after being moved to Constantinople. The Roman copyist was not working from the statue itself but from an inherited visual tradition, generations of sculptors passing down a way of rendering Zeus's face and bearing that had already drifted some distance from whatever Pheidias actually made.
That makes the Otricoli head evidence of a lineage rather than a faithful record of a lost masterpiece, and honest scholarship treats it that way. Nobody today can say with certainty how closely this head resembles Pheidias's Zeus, only that it belongs to the broad family of images descending from it, distinguished by a particular way of carving the brow and mouth that later became a kind of visual shorthand for divine, fatherly authority.
There is something fitting in that uncertainty surviving alongside the image itself. A cult statue meant to represent the king of the gods was always going to outrun any single artist's hand, copied and re-copied by people trying to capture an idea of majesty that had, by their own time, already become more legend than living memory.