For years I had this 3 X 2 1/2" spool that was marked with a simple B. I could never find any info on it except of course B was a trademark for Brookfield insulators. I came across an electrical porcelain lot awhile back that had a lot of old pieces in it and a variety of markings. In that lot were two nail knobs and a wall tube that caught my eye. The wall tube and smaller nail knob were marked with a B. The larger nail knob was marked with a B inside a Pentagon shape. I had seen this before in a online catalog and found it. It is the marking from Barber Electric Mfg. Co. Massachusettes which was founded in 1915 and is still in buisness today. Seeing that these pieces came from the same area from a seller there it's a no brainer. I love it when history info comes together and presents itself. So I can now attibute this marking to them. As to who made the porcelain pieces, that's another mystery. The large nail knob measures 2 1/8" H X 1 3/4" W, the smaller nail knob measures 1 1/2" H X 1 3/8"W, The tube is 3 1/2" long. Neat.