Which is somewhat nonsensical, of course - they can already separate out the steel pennies magnetically, and it would be pretty pointless to have all of the rem

Which is somewhat nonsensical, of course - they can already separate out the steel pennies magnetically, and it would be pretty pointless to have all of the remaining pennies after that separation step float. If anything, they'll have the less dense non-steel float and the denser non-steel sink.