Here is the unique BROOKFIELD insulator I have with the strange inner recess petticoat. I have never seen any other one like it and am interested in any information anyone can give me about it. I can't imagine how it could have been made like this and also would like to know if anyone has one like it. The insulator to the right is a regular BROOKFIELD signal next to it for comparison of the inner petticoats. The recess can be seen to completely circle the interior and the petticoat jutts inward kind of like a fog bowl.
*This has been determined to be a very rare manufacturing defect possibly caused by an open bubble that allowed just enough glass to form the petticoat. Thanks to all the people who answered my request.