JACK WARNER. Bold signature and inscription, “To John -/San jose Calif/Jack Warner, “ in blue fountain pen on a 6×4 white index card. Very fine condition, with a small magazine photograph affixed at the top right. Undated on the reverse side. John Verzi collection. A founder and co-head of production at Warner Bros. for 45 years, Jack Warner was one of the most influential of the Hollywood moguls during its golden age and largely responsible for the punchy social dramas that largely defined the studio’s output in the 1930s.