NINE choirs of angels

Christian tradition suggests that there are three hierarchies of angels, each of which is divided into three choirs. The design for the ninth chair shows the hierarchies arranged in their appropriate three tiers. The circle at the top of the "9" contains a globe, symbolising God. The globe contains a rainbow symbolising a throne.

"...behold a throne was set in heaven,
and one sat on the throne...
and there was rainbow around the throne."