Yes that's it. I just read this on Alen's site. "Sometimes inverted" but still don't know how that happens. I know I'll be tossing in my sleep tonight.
M.F. Christensen marbles have a diagnostic trait known as the "nine and tail." Basically, as the glass was twisted from the furnace a nine-shaped spiral (sometimes inverted) was left on one pole of the marble. Often, this "nine" exhibits a "tail" that spirals around the marble and either ends at the opposite pole or terminates somewhere in between, even occasonally looping back to the point of origi