Those pictures look very similar to the many failed Chance cutouts that I have run across. Sometimes, they will crack circumferentially around the area of the mounting stud, and some have the stud burned off completely.
Imagine what could happen on a three phase bank with one of these breaking while you are on the pole or in the vicinity in a bucket. Even worse, if you are in your hooks opening a cutout on a loop feed after the loop has been closed at another location, and the bottom of the cutout breaks off while still being hot.
Why isn't there more safety bulletins issued about these? I try to tell everyone I work with about these cutouts.