That's just another form of lightning rod insulator! I know nothing about them, unfortunately, except exactly what the use was. I do know that what you've got there appears to be an older style, and that the interest in lightning rod insulators is booming right now! Good find!
Frank, I'd say it was a right good day. Anytime you're finding something new and adding to the collection is a good day. Love the litte cup, has to be from a doll tea set. Too small for a child tea set. I'm crazy about an embossed med. I have one version of the Bell's , not sure which.