This is definetely the oldest insulator I have dug. I reads C & P Tel Co. I would like to know how much it's worth or any information you have on it. Thanks, Joey.
I can't tell you about value, but I've seen them around since
I once worked with C&P Telephone when I was much younger. In my opininon, they aren't common.
It looks aqua from the picture, the style number is a CD 121, they book at $5 - $10 in the latest price guide. There are 2 embossing variations, one with a number on the dome, one without - same value for both. Different colours bring more money - blue books at 10 -15. If you could find one in Green or yellow green the value goes up to 100 -300.