Some of the high limit tokens, even the $100's sometimes, have precious metal content. There are many sterling silver $25's, and quite a few 100's that have 14K gold center inlays. There's supposed to be a solid gold Caesars Palace token, but I've never seen one.

There is a gold token from Monte Carlo, Monaco that was made by Franklin Mint many years ago. I have one in the issue package, but don't know whether they were actually used in play there.

As gaming tokens are passing into desuetude, if you like the 'hard money' casino collectibles, better start picking them up now. Janice's list is the place to start to see the magnitude of your task, at least in Nevada.