Also picked this up at the antique faire. It was in the box of insulators. The flat spot on the porcelain ring is the firing rest. To me it looks like an insulated cable support, but how the bracket functioned is a mystery to me. Any ideas? catalog cut sheets?

Thanks to Dustin Logan for finding Bill Ostrander's photo of the insulator and bracket in use on a sign. Notice the different arrangement of the strap and connecting link.

Click here [id=351100531]

Apparently, in Bill's photograph the insulator is not being use to spec. Ron Jenkins tried to explain to me how they were used but Ron talks like a retired lineman so I didn't understand him.

Here is a Line Material catalog cut sheet provided by Elton Gish that explains and illustrates how this Take-Off insulator works to add service drops. Click here:

[id=433148485]

I get it now Ron!