Japanese metal alloy: iron and silver?

I just spoke with an collector of Japanese objects. She mentioned
the Japanese alloying silver and iron, but labelled it shakudo which
I know as 2-10% gold and the remainder as copper. I would NOT call
anything shakudo that is not patinated navyblue/black and resembling
fine lacquer. The Tsuba I have handled were that. I see whole vases
that are not patinated called shakudo, shibuichi maybe, but shakudo,