Just trying to learn the U system and finding out what some of my porcelain actually is, but can't identify this one. Its a nice brown glaze but was fired standing on the dome. The petticoat is recessed and very long and thin resulting in cracks and distortion. It is 2 3/4"x3 3/4".
I suspect your insulator is a U-1352 from Canada: http://www.nia.org/general/pifous/text/u1352.htm
These are fired with a top rest.