I just got this thing on eBay... I bid on it because I could not identify it, and that bothered me. Now that I have it in hand, I don't recall having seen one before, and I can't find a listing in the book that seems to fit it. It was described as a CD 162 with no embossing, and that may be as good a classification as any, but it is also close to a CD 160.4 in appearance (but not exact). Measurements are 2 7/8" wide by 3 1/2" high. The threading appears to be similar to some American Insulator Co. products and that is my guess as to it's origin. Has anyone seen one before? I'd really like to hear any opinions or insights! It was dug in a dump in New York. Here is a picture of the base [id=85680713] (note that this insulator DOES have an inner skirt)
****Answer: After sending this insulator to John McDougald and then to N.R.Woodward, it has been officially classified as a CD 160.4. So far it appears to be the only one like it known. A completely new listing! The general consensus was that it is an American or Oakman product.