These actually are two sets hooked together. If you look closely there is an open end on the bottom of the two connected assemblies.

These were used individually (and not necessarily in pairs as shown) for "hooking" the eyelet of the applicable street light fixture hood to the hanger assembly.

Lots of electrical insulation was necessary because these ran on street series circuits. Whenever there was an open in the series loop the voltage automatically would become rather astronomical unless there was a safeguard to prevent this during a fault or open break somewhere in the line.

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