This group of unusual and colored fence insulators were manufactured by Illinois Electric Mfg. Co. and Superior Porcelain Co. The first four were made by Illinois. Triangle M/99, Triangle M ink marked spool, M marked Lt. blue nail knob, M marked cobalt nail knob. The M stands for Macomb Illinois. The last two were made by Superior. S.P. Co./666, Superior 5 1/2. Neat.