I staged this photo showing how the insulated bracket hanger brackets for early street lamps worked. The two conductors for the lamp would be attached to the terminals on top of the lamp then tied to the spools on the wire spreader and would then be draped over to pin type insulators on the pole . A metal link chain or rope would loop through the pulley and go down through the hollow center of the hanger shaft and then attach to the round bulbus point at the bottom of the hanger shaft. When you pull the chain tight from the ground it unlocks the hanger from the pulley and allows the lamp to be lowered to the ground for maintenance. When you raise the lamp back up the insulated hanger automatically locks into the pulley and allows the chain to go slack.
This set up was a very ingenious way to deal with the early carbon arc series street lamps which needed weekly maintenance to keep them working. It made the job much safer for lamp trimmers who could just put out their insulated platform stand and service the lamp on the ground.
I fear I could get sucked into the bottomless pit of collecting hanger brackets for these things There are so many different designs !