The original Contenders are not really as strong as the old literature supposes. Many people have stretched those thin frame sides and/or widened the hinge pin hole using very hot loads or powerful wildcats. The G2 is much stronger. the Encore is stronger, still.
They are not as strong as a G2 but in all of the rounds they are chambered for (many being centerfire rifle rounds originally) I have never heard of one getting damaged by a 357mag.