In my possession I have this "mushroom" style insulator, that originates from a collection of insulators from a technical school in Belgium. It is very well made of high quality porcelain, with thin and delicate walls of the umbrella and skirt. It have a hole thru it, like a spool insulator. The origin/use of this insulator has been, at least to me, unknown up until now. While searching the net, I came across an article in "Scientific American" from december 18, 1880. In the article this insulator is pictured as a "New telegraph insulator" for use in South America, especially where a bird called Hornero build its mud nests. The link to the article is: http://www.gutenberg.org/files/21081/21081-h/21081-h.htm#article20 Next picture [id=193473661] shows the illustration in said article.