Found four of these on a crossarm in an insulator dump and thought they were interesting. I can't find any mention of them on the internet nor on the Fred Locke web page. They are hollow inside.

Dimensions:

Total length from top of lead to bottom thread of steel post: 15" Total length of lead: 2 1/2" Pin Base to beginning of lead threads: 5 3/4" Widest width at base: 3 1/4" Width just underneath lead threading: 1 1/4" Weight: 5.0 lbs.