It is fairly easy to determine what types of insulators were made in this manner, by examining the character of the "straw lines" on or near the dome. Stringers do wind up falling into molds, and there are also folds, but ladle gathers result in a different appearance. The dribble and stringer result in a pair of "straw lines" which form a "V" shape. As they diverge, they fade out. on this CD 143, you can see that the glass was not very hot, as the dribble has only a slight taper to it.