N. R. "Woody" Woodward is the author of THE GLASS INSULATOR IN AMERICA, 1988 Report and developed the Consolidated Design Numbers identification system for glass insulators. 

The following questions come from Steve Kelly of Tempe, Arizona

QUESTION: What is the reason for the cross top design on the CD 141 and CD 208? 1 have a CD 141 that has a wire rub mark on the lower ridge of the side groove. It would appear that the line was tied to the side and not to the top.

CD 141 and 208 were designed for telephone lines constructed in mountainous territory. It is quite true, as you suspected, that many were used with the usual side tie. I've seen them often that way. But in cases where there was a strong downward pull due to a sharp drop in the line, as for example passing over a bluff or ravine, a supporting tie could be placed over the top to prevent the line from dropping; or the line wire itself could be secured in the top groove. Many of these were used in certain areas: and where there was no special need, the wire was tied in the usual manner in the side groove.

QUESTION: Any explanations on why they required the CD 128.4 design? Where were most of these found? Who were these manufactured for? What does the SB embossing stand for?

Unfortunately little is known about the SB carrier insulator, CD 128.4. They were made by Owens-Illinois in 1938 and obviously were intended to provide extra security in supporting the line. I've never seen any on the line, and have heard of them being found in the Midwest and the West. They would most likely be an experimental piece made for Western Electric: but we have no proof.

QUESTION: Were the purple tint Maydwell CD 106's intentional?

Maydwell insulators were made of essentially clear glass except for the white No. 20 made for Pacific Gas & Electric. Tints of yellow or pink were the result of variation in the decolorizer formula.