In the absence of any help from the manufacturer, is there a sure, non-destructive way to determine the composition of string windings? It's remarkable how many sets have NO indication on the packaging or websites, plus one always accumulates mystery strings. I can usually tell stainless steel by the dark gray, dull finish, but I'm not too clear on separating nickle from nickle-plate. There are often strings that are not obviously one thing or the other, too. Stainless steel roundwounds are so ruinously destructive of frets that I won't have them in my house, but nickle-plate over steel doesn't always assure any less damage as the plating can be very thin. Thanks for any help on this.