These are some of the insulators I have cleaned so far fome hunts monday and tuesday. I have found a half dozen of the CD 210s on the line I hunted tuesday along with brookfield CD 152 and hemigray 152s and hemingray 145s. Can anyone e-mail me info on the 210s were these used for telegraph use and the 210s I have found only have the marking postal on top of them does any one know who made these.