Insulators Home > Insulator Styles > Glass > Threaded > CD 301
US Patent 700,463 of May 20, 1902 by William J. Walther of Boston, MA "for ribs under the top skirt of power insulators to add strength" was implemented in CD 247, CD 301, CD 315, CD 321, and CD 333. : http://www.nia.org/timeline/1900.htm
Insulators Home > Insulator Styles > Glass > Threaded > CD 301
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