The CD145 "Beehive" style insulator was adopted as the Western Union standard in the 1880's and remained that company's primary telegraph insulator until the design was replaced by the CD152 around 1910.
Two patent dates adorn the rear crown of this colorful Brookfield piece. The Nov. 13th, 1883 patent covered the addition of an inner skirt to make a "double petticoat" insulator. The Feb. 12th, 1884 patent was for the design itself of this type. Both of these features were Samuel Oakman innovations.
This one was found in north central Mississippi during November 1999, about 60 miles from my home, where it had been perched on its crossarm for over 100 years.