Dome Glass

Examples of dome glass, in which the pin hole is very low resulting in a large amount of solid glass at the top of the insulator. This is caused by the mandrel that makes the threads not being fully inserted into the mold. On later presses, the mandrel automatically adjusted to how much glass was gathered into the mold, so if there were too much glass the mandrel would not be inserted as far leaving more glass in the crown. While not especially rare, these are valued by collectors.

CD 112.1