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COVID MASK? Us Patent 4666148A

Electric device for indicating the awakening of persons buried alive  Patented July 3,1900 by Walter J Mcknight Patent #No. 652,934. ELECTRIC DEVICE FOR INDICATINGTI-IE AWAKENING OF PERSONS BURIED ALIVE. This invention was to indicate the awakening of persons buried alive. This device adapted to be connected to coffins for attracting attention to and indicating the…