This insulator was shown to Caleb Thimmel at the Eagle Cap 2009 show and he said that it had an unusual cable groove. It was obtained from Howard Banks and went into my wife's collection. Notice the tilted inner petticoat and threads.

The strange thing about this insulator is that it has some striking manufaturing charicteristics of Brookfield made insulators. I would not be suprised if this insulator was made by Brookfield and was exported.