I got a 1957 silver certificate one dollar bill with star next to the series number. Someone ask me to sell it to him but I don't even know how much it worth, please help!

https://www.facebook.com/media/set/?set=a.487623062619.270468.551172619&type=3#!/photo.php?fbid=10150730729932620&set=a.487623062619.270468.551172619&type=3&theater

https://www.facebook.com/media/set/?set=a.487623062619.270468.551172619&type=3#!/photo.php?fbid=10150730729932620&set=a.487623062619.270468.551172619&type=3&theater

You can find a picture of the bill here