(Κόκκος), an Athenian orator or rhetorician, was, according to Suidas (s. v.), a disciple of Isocrates, and wrote rhetorical discourses (λόγους ῥητορικούς). A passage of Quintilian (12.10) has been thought to imply that Coccus lived at an earlier period than Isocrates and even Lysias; but it seems that Quintilian is speaking of the comparative distinction of the orators he mentions, rather than of their time.
[P.S]A Dictionary of Greek and Roman biography and mythology
Smith, William
A Dictionary of Greek and Roman biography and mythology. William Smith, LLD, ed. 1890