CPR porcelain double groove insulator, most likely a Pittsburgh product. Good strong dome embossing for one of these. This insulator has a ¼" flake off of the underside of the upper wire ridge, a crazing line from the base to the first groove and a couple of base flakes in an area the was partially glazed over. These insulators are getting very tough to find. The price is $50.00 which includes shipping within North America. Email for more info - Thanks for looking.