Back in March while returning home from the Shrewsbury show I picked this CD 104 up in a junk shop for a dollar. I don't have any other insulators with a bubble this large. The bubble opens into the threads and causes the skirt to bulge out on the inside. The insulator was stained from being buried and the huge bubble was full of dirt. It took a while, but I was finally able to get it cleaned up enough to hand it over to an expert for a proper cleaning.