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There is 1 insulator style embossed with B & O that has any type of wire groove and any number of petticoats, shown below.

PLEASE NOTE: Insulators embossed with "B & O" were also manufactured by other glass companies, not just Hemingray. This database will only show the styles that were manufactured by Hemingray. Some insulator styles shown below may have been produced by other glass companies as well.