Terminator II question

I am considering buying a Terminator II but I have one concern. Why do they use pennies as contacts, when most are not solid copper? Every penny made since '82 is zinc, thinly plated with copper. I even read on one Zapper site that the copper can react with sweat and eventually etch away leaving you with zinc contacts. If I pay $100+ for one of these things, I at least want my 2 cents worth of copper!