Speaking of Atlantis, when I was there in 2004 they had one design in all of the machines. I played and played and got nothing but the Minah birds.

I suppose they had new ones on order and I was just unlucky to be in town at the wrong time.

On the question. I have found casino chips that were approved, and never made. So the other part of the answer is, that just because the design is approved, it doesn't mean that the casino will have them made.