If you're refering to the seam this isn't damage but how they were made by St. louis, the more usually seen method was to make a ball of canes, reheat it and then draw it into an egg shape, this results in very distorted canes, you will often see late Murano egg shaped design with these distorted canes.
St. Louis made theirs as in this weight and the one I had by cutting one part ball and one only slightly stretched section and then placing then together to minmise this distortion, this was then encased in the clear outer glass.