The $1 tokens I have are composed of silver. You can find examples on Dan's website:

http://www.casino-tokens.com/SilverProofTokens.html

The $1 Ponderosa can be seen on the Silver Strikers website here:

http://www.silverstrikers.com/Web/Catalogs/Tokens/Nevada/PonderosaREnv/Ponderosa-REnv-Token-Page-01.php/

The tokens are also listed in Earl Donley's 'A List of the World's Gaming Tokens' as having a silver composition. And if you take them to a local metal reclaimer who has a X-ray fluorescence spectrometer, they will confirm the silver content without damaging the token. Otherwise, they will try to file the edge of the token and utilize acid to confirm that the token is silver. In 1965, the Franklin Mint produced a full-proof collector's set of $1 casino tokens composed of .999 silver utilizing the same dies used to create the casinos regular slot tokens. You can currently find a set on sell at ebay, see #201479162531.