It depends on who you listen to...

To some (like ME)... I consider a chip "obsolete" when a casino WILL NOT redeem them. Either because the casino is closed... or that the casino has posted a redemption period and no longer recognizes that chip as a "debt" to be honored by the casino.

Now... other people feel that a chip is "obsolete" when the casino runs out of them ... or whatever.

Good question... hope you get some feedback on this question!