My apologies, Jens
In my zeal to show references (other than my bad memory), and in trying to keep to the basics... I do not wish to overwhelm anyone who is not ready for the info, some of my post may or may not be as helpful as intended (maybe a little to basic). Sorry.
What I was trying to say and show... the only real source for "nickel-iron" (that which is already combined) would have a cosmic source, like a meteorite. The mining literature from the Luwu area suggest separate nickel and iron ores... unless someone else knows and can post a source on a non-cosmic source, I would be most interested in learning about it.
I think karma, fate, chance, circumstances or what ever term you want to use... placed a "workable" meteorite where it did and made the Keris a very special and unique weapon that it is.