Hello all, I'm really late to this one, and missed most of the fun.
It sounds like (Served Litz wire) it's stranded wire with a silk or nylon woven in or wrapped around the copper strands. It's mostly for added protection during pulling on install. It keeps the fine copper strands from stretching. The outer jacket will say something like (14/36 Single Silk or Nylon Served) = 14 strands of 36 AWG. Hope that helps a bit.