Here's something very similar to the Holmes Tree Insulator. It was patented in 1890 (see [http://reference.insulators.info/patents/detail/?patent=U-418766]) by J. Brodie Smith. Originally made by the H. E. Swift Manufacturing Company, beginning in 1894 it was made by the Brodie Electric Company of Manchester, NH. This version doesn't quite match the patent drawing, but advertisements from that time show drawings that exactly match the picture above. The ads actually show what appears to be a CD 162 as the heavier duty version, and a lighter duty version is shown with the CD 114.2. The other existing examples of the Brodie Tree Insulator I'm aware of have a CD 112, embossed S.B.T & T. CO, and a Brookfield CD 112.
The metal yoke that surrounds the insulator has an adjustable pivot -- the assembly could be screwed into a tree and then the angle of the insulator could be adjusted by loosening the screw, moving the insulator up or down, and then tightening the screw back down. The porcelain pulley at the bottom is attached to a metal bracket that is cemented in place in the insulator. The above example is a CD 162 STAR in green, presumably made by Novelty in the early 1900s.
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