Okay, Rick... here we go again...

What if a current casino starts using rack chips from a closed casino? It happens. Are those chips "still" obsolete?

I personally like the concept where a chip is obsolete if you are unable to buy it, under normal circumstances, from any casino, even if they were to have them at the cage. (I threw in the "under normal circumstances" part because theoretically, you could, say, walk into the Sands in Atlantic City right after the guy in front of you cashed in a Brighton chip, and talk the cashier into selling it to you. To my thinking, the Brighton chips are definitely obsolete, and any definition that says they aren't can't be valid.)