This porcelain block insulator was made by the Pacific Pottery Company of Sacramento, California. It is made of a terra cotta clay material, glazed and fired. Pacific Pottery Co. also made other clay base products including terra cotta sewer pipe. This piece was used on the first telegraph line to cross the Sierra Nevada mountains from Placerville, CA to Genoa, NV. The line was built by the Placerville & Humboldt Telegraph Co in 1858. The pictures here include the side bracket for that installation. This is only the outter portion of the bracket that was exposed on the tree. The exposed portion was cut away from the tree rather that cutting into the tree to get the entire bracket.