To Determine Whether Six or Nine Blades
Ben G.,
To determine whether the fan has six or nine blades, you can either turn it on and listen to the tone and pitch of the vacuum (if you don't feel like removing the Adjust-O-Rite), or you could remove the Adjust-O-Rite and look with a keen eye inside the motor.
If the pitch of the motor is higher than usual, it would have nine blades.
To compare:
Royal with 6-blade fan:
Royal with 9-blade fan:
Yours should sound like the one in the second link.
~Ben Edge