This is THE original clapperboard that Steven Spielberg is holding in this now famous photo of the behind scenes of the movie that is known as the first summer blockbuster, JAWS. With E.T., the most important movie in his career.
The last scene shot with this clapper was the reshoot of the Ben Gardner head in Verna Fields pool. In that scene Rexford Metz was the director of photography.
I attach one photo with several matching points.