Although not normally accepted as a way to destroy obsolete chips today, that was commonplace in the 50's through 70's. The first I know of was the Sahara Tahoe/Reno chips that were buried in concrete during new construction. I think those were in metal drums, as many are pretty nice. These were mostly $1 and $5 chips. A few $25's, but the Reno 25's were never found in the dig.

The best known is the disinterment of several generations of Dunes, LV chips. I believe the new construction of Bellagio in the 90's surfaced them.

The Sands is one of the more recent digs, as mentioned in an earlier post.

Something different was the unearthing of thousands of Playboy, A/C chips in Hernando, MS at the site of a company who was paid to "destroy" them. Instead, they played Hernando's hideway and just dug a hole and pushed them in.

There have been others, but these come to mind to me.

Because of the suddenly increased quantity of old chips, and the likelihood they will be damaged and discolored from their burial, the chips don't sell for much. I have bought a few of the less common Sands baccarat chips that way but the undamaged ones still sold for hundreds each.