I can offer no possible explanation for what you're looking at here. It is a complete CD 155 Kerr DP1, with an extended and protruding base. This insulator could not have been made in a standard mold - the top plate of the mold, which forms the bottom of the insulator, had to have been extensively modified to allow the insulator to be molded like this. The extended protruding base is of consistant quality for its entire diameter, it was obviously molded with the insulator, not added later. I believe everyone will agree that this is truly ridiculous. From the collection of Pete Horner.