United States. Patent Office · Washington, D.C., Govt. Print. Off. · leaf 328
R. A. BOSWELL. AMPLIFYING TDBE, APPLIOATIOH PILED SEPT. 26, 1910. Patented July 11, 1911. 997,265. 2 SHEETS-SHEET 1. … ^Wvtvtcooeo €ltt&VYWlj$ COLUMBIA PLANOOBAPH CO.. WASHINGTON, D. C. L
Phonograph · Patents
Internet Archive · Smithsonian Libraries · Public domain (published before 1931). Free to use for anything.
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