In the persistent effort to find out what the metallic white stuff is called that lines a peanut shell, first I offer what it is not:

b : the persistent calyx or involucre that subtends some fruits

And it's not the albedo either. And it's definitely not the bagasse. And I'm not talking Spanish peanuts either, though they might have that same white metallic inside-shell finish that field peanuts do here in the US. (Are Spanish peanuts really Spanish?)

Best research,
WW