Here's a photo of the CP CO incuse. This does stand for "Canadian Porcelain Company", right? The glaze sure looks different than ordinary Canadian Porcelain pieces.
[id=127928395;See here] for the full insulator.
Update! Upon conversing with Mr. Gish, I was told that no M-# had been assigned! So, he asked for a better profile shot, so that a drawing could be made, and I was told this piece has been assigned the M-2244 listing! I'm ecstatic! However, I must keep my composure - other collectors have told me they have, or have seen these before. Paul Axeman has 2 examples, both marked and unmarked, and Phil Ort has a marked piece! Several collectors also confirmed that it is of Canadian Porcelain manufacture, especially Paul Axeman, who informed me that he had dug pieces at the Canadian Porcelain dump site. Thank you, everyone!