Here are two porcelain service entry insulators, both made up of two pieces of ceramic that connect together. These would mount on top of the conduit to bring service into a building or house.

First is a green glaze ceramic in good condition (6" diameter and unmarked) -- the ceramic base is bolted to the dome and has slots for six wires. $30

Second is a brown glaze in two pieces (sleeve and top) that link together for the entry (6.5" diameter and unmarked). Small bruise on the side of the top part. $15

Actual postage additional