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A magic lantern slide (glass, paper, tape, 3x4 inches) uses the latest news from Hollywood (in this instance, the short-lived marriage of William S. Hart and Winifred Westover on December 7, 1921) as a template for an advertiser (in this instance, Al J. Feix Dairy Supplies).
Considering the subject matter, it dates to late 1921 or early 1922. Issued by Paramount Publicity Corporation of New York City.
The use of the colorized image of Winifred with the flowers helps us date the underlying BW photograph. It's one in series of Winifred-with-flowers photographs made by Hoover Art Company of Los Angeles. (We know who made it; we don't know when.) At least one photograph from this series was used later, on a movie star postcard published in Sweden no earlier than 1925.
Lantern slides were the movie trailers (and advertising pieces) of their day; they were projected onto the screen with a magic lantern, which was the slide projector of its day.
LW3691: 9600 dpi jpeg from original lantern slide purchased 2020 by Leon Worden.