Found class ring cast trees would these be silver or a lesser metal ?

I did a job in 97 and found some casting molds. Upon breaking them open found "class ring tree's" inside. broke most of the plaster away . now i noticed they r showing signs of rust. what metal would these be. could the rust be from metal trasfer since i took a hammer to one to beat the plaster off. I,ve been told they r silver , no magnet attraction but im not sure.