The variation is in the brown ribbon. Look above the "a" in casino and notice how much white is showing between the blue and green ribbons. I have seen several of the more white showing ones and they all also have the thin line of brown on the blue ribbon. It looks like a scratch in the scan, but isn't. Also look at the brown ribbon under the "M".
These poor chips have seen a lot of play. Most of my traders have small cracks in the inserts. Like the one on the left at the one O'clock position. The right one at ten O'clock.