Dug on a hillside.

Elton Gish replied:

"...I'm fairly sure it is the Stone patent – 295,073 (1884) – for a telegraph wire supporter."

"Your insulator appears to have been made of wet process porcelain or at least a fine grade of dry pressed ware. In the 1880's, the only companies making that type of porcelain was Union Porcelain Works (Greenpoint, NY, which is Brooklyn now) and Empire China Works also located in Greenpoint."