Glass Threadless Insulators

The idea of threading glass insulators to secure them to pins was patented in 1865. Before that time (and for a few years after by companies that did not license this patent) insulators were made without threads and were wedged on the pins by numerous means (Burlap, tar, and other materials were used to help the insulator hold to the pin.). Threadless insulators are assigned CD numbers from 700-799 and glass block styles from 1000-1014. There is a large variety of threadless insulators known, and they are all relatively scarce as most were taken out of service over 100 years ago. The following is an excellent reference on these styles:

A History and Guide to North American Pintype Glass Insulators - John & Carol McDougald

Note: Click on each insulator for larger pictures and more information!

CD 700 through CD 796 are threadless pintype insulators