Recently I was searching around for a core and some cylinders to cobble up as a teaching aid for my students, so was looking for somethubg rusted out, essentially scrap that I could tart up.
But.........apparentlky the metal used in a core is of such prime quality that they fetch over 5 grand at a scrap metal yard. Thats what i was told at least.
Much more valuable than copper it would seem.