I have this on the tip of my tongue... but I can't place it. Is this a metal insulator that holds a trolley wire between it's "fingers" and they are bent over around it?

What would be the approximate date of usage?

ANSWER:

Several people responded. Thanks. This is an insulator for a feeder wire, commonly used on trolley systems. Rather than a tie wire, the "fingers" on the insulator are bent over the large diameter wire. It would likely be for a 600 volt DC cable in 300 or 500 solid copper wire or 750 to 1000 stranded copper.

Although the outer shell is metal, it has a composition core that provides the insulation. It was used about 1890-1910 or so.

This insulator is very similar to patent 520,855

http://reference.insulators.info/patents/detail/?patent=U-520855