Provo-type electrical insulator, ca. 1897
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This style of glass insulator was originally made in 1898 for the Telluride Power Transmission Company in Provo, Utah, which used it to construct a long high voltage line.
It proved unreliable at high voltage, but worked well at lower voltages, and remained a popular technology for 22kV transmission lines throughout the United States until porcelain multipart insulators were developed.