[dave9t5]

I think they mean a brass core.......not copper, a common error.

 

This is a common translation issue from Chinese.  Since brass is an alloy of copper, it's not totally incorrect (i.e. copper alloy).  Sometimes brass is wrongly translated to bronze, which is less correct.  Brass is an alloy of copper with zinc, bronze is an alloy of copper with tin; there should be no ambiguity.  

 

Another jarring translation is that steel is often translated to "iron".  Also, technically not incorrect (steel is an alloy of iron).