Observation device
United States Patent 2169874
Inventors:
Hardt, William G.
Publication Date:
08/15/1939
Export Citation:
Assignee:
Hardt, William G.
Primary Class:
Other Classes:
359/808, 359/823, 359/809, 359/894, 359/738, 49/171
International Classes:
E06B7/30; E06B7/00
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