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Filed: Oct. 5, 1899
Issued: Oct. 16, 1900
Inventor: Chester W. Brown
Long before the days of digital cameras, photographers used metal or glass plates to capture images. To help these early photographers, Chester Brown invented a device that could be "carried in the pocket or otherwise for determining the length of time for exposing photographic plates according to the rules of photography applicable to varying conditions…"
Image taken from U.S. Patent 659,727 - Digitized by Google