I did some research on here (not for hours though). Upon separating/sorting my ww's I developed a notion that all stick on ww's are not created equal. I know obviously that some are steel, zinc, aluminum etc.. But aside from all the soft, obvious pure lead ones there is one type (painted grey) that cuts similar to a clip on. I've attached a pic. Is it possible this type has same ingredients as the clip on ww's?