Another view of the rolling pin whatzit. What is it?

According to Douglas Moody (and others)... Those copper ends are one half of a standard "automatic" splice. Automatic splices are used almost universally to splice overhead conductors. You just push the conductor in each end and those spring loaded jaws capture it, and the current flows through the splice body. There is also an automatic dead end assembly that works the same way, essentially one half of an automatic splice with a way to attach the other end to an insulator. I have not seen your example, but maybe it's a "Line Break" automatic splice.

Here is one in use: [id=126326499]

This info recently added by Bart Magoffin: The nice thing about this "Line Break" is that it can be added to an existing line without splicing in an extra length of wire. If a standard guy insulator was used, extra line wire length would be needed to loop through the guy.