Lol, rust preventative.... more like a recipe for galvanic corrosion. Speaking of 1943 cents, has anyone come across one with anything you'd call "toning," as opposed to "corrosion"?
They actually have a science award for this! A few of my daughter's friends ended up doing this and they got an award from Tootsie: http://tootsie.com/how-many-licks/
I like to cheat and get the pop with the outer candy part off-center so the dark tootsie center shows through.