Larry; A $200 one pound is the buy back from the issuing casino. Your Wild Horse has no value stated on it. So it may have been sold at the gift shop for $60-$75, but will they buy it back? If they will then that will be the worth of it. If it's .999 fine silver then it's what silver is worth that day. Or what someone will pay you for it. You may want $200, but if you can only get $60 then that is what it's worth. It's supply, and demand.
Why don't you contact the casino, and ask the cage about it. Did it have a number on the edge or something that told you the weight, and the pureness of the silver. If it doesn't show that it may only be copper layed with silver.
And then tell us about it.