I sometimes see 1988 Marshall Islands Space Shuttle Discovery five dollar coins being sold on eBay as being made of silver. Sadly they are not made of silver but of copper-nickel and are of very little value. Apparently these coins are not legal tender in the Marshall Islands so they are not even worth the face value of 5 dollars.
There are some similar higher dollar value Marshall Islands coins that are made of silver, but not these $5 ones: