Being a home inspector, I have the opportunity of seeing knob and tube insulators almost every day. I have compared them to what I have and the results...not even close. My "bead" is more of a mill stone or (grind stone) material heavier than ceramic. It is exactly what a miniature mill stone would look and feel like. If this is not a bead, could it possibly be a tool used to make beads?
I will continue my research starting with the mentioned article by Lester A. Ross.