These primarily are a lag screw type service drop insulator. The newer styles are a bolt on type that at attach to the service drop mast. Colored porcelain is very unusual for this style of insulator. Originally it was screwed into the house siding or rafter closest to the meter base service mast and used as an anchor point to hang the service drop from.

The longer the service drop span or the weight of a general service 3 phase drop then the larger and heavier duty the insulator was required to be. Some of these served telephone service drops only and were very small in size compared to the power sizes.