Here are two large power insulators - both are uniparts - actual postage additional:

6 1/8" tall top groove unipart with three skirts -- VNM+ -- inkstamped with the bullers logo and a 1952 date -- inkstamped on the other side with two stars over 23 7 52 -- $35

6 3/8 tall round toped unipart with three skirts -- VNM (just sone very light scratching) -- inkstamped with the bullers logo (year hard to read) -- $35