According to the wikipedia:
Some were inlaid or banded with strips of iron or other metals for
And the link they give for reference #11 is from Jo: Art of the Japanese Short Staff, Dave Lowry, Black Belt Communications, 1987 p.22.
They link to an Amazon preview which says:
Occasionally too, the length of the bo was inlaid or banded with
strips of iron or other metal. This increased the strength of the bo
considerably. Most techniques for countering the bo by well-trained
swordsman involved his using the katana to slash at the wooden bo at
an angle that would hack through it, cutting the bo down and
significantly reducing its effectiveness. With the protecting bands or
strips of metal, the weapon was much more difficult to chop or cut and
the bojutsu exponent was at a better advantage in the encounter.
So there's your answer.
As for getting your hands on a bo staff like this, they're pretty rare. I wasn't even aware they existed until you mentioned it. And I was unable to find a picture of one online.
The 9 bands you mentioned make sense for Kukishin Ryu. It is called the "9 Demon Gods" school. The number 9 has some mystical significance in many Japanese martial arts.