BamaLaw if I am thinking of the same 'Century of Champions' ball that you have, that's a gorgeous ball to start with, is it the one that has 2 white panels and 2 panels that have what appears to be 'elephant' skin? I have one like that that has 3 white panels, and the fourth has the 'elephant' skin. It doesn't have the Century of Champions logo, it has the old-style Elephant running through the A logo.
As for the 1966 ball, obviously the 2 biggest factors are going to be the condition of the ball itself, and if it has Bear's signature or not. Then you also have to consider the condition of the signatures, if they are clear or not.
IF you had a ball signed by the team and signed by both Bear and Snake, and if the ball and sigs are in decent condition.....I would say over a thousand easily.
If you have a ball that's been signed recently like the 1961 ball, and if it has Snake and most of the rest of the team, I would say it could easily go for $500 if you sold it, and maybe push a thousand if you had a couple of bidders get in a bidding war. Wouldn't surprise me if the 61 ball went well over $500, especially since I've seen nice 1992 balls go for $250-300.
And I agree, the 1966 team was the best ever!