This is a threadless pintype porcelain insulator. The pictures to the left show both sides of the insulator as well as the base. There is a 1.5" x 1/2" chip on the base, a 1/2" x 1/8" horizontal chip on the base with a 1/4" round flake on the inside of the base opposite this chip, and a 1/2" base crack. There are also two short upper wire groove cracks that were made during manufacturing. A fine line runs from the smaller chip up to the wire groove. You can see it in the top right image to the left.
I had the good luck to purchase this in an auction in 2014.
Since there are so few of these, I believe it is important to document them and preserve their provenance.
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