Hi Xas,
I've been thinking about this one a bit before replying to your post. I've not seen chromium plating before on a Lumad piece. I have seen a nickel-plated
kris blade, but not chromium. So that's a pretty unusual piece. The darker surface areas look like oxidized iron or steel to me--in other words rust--perhaps old and stabilized, or perhaps the reason why the blade was plated in the first place. Metal plating is an electrolytic process, and chromium plating usually requires a cyanide bath. Both of those features are fairly sophisticated (and dangerous) operations, not something you would find readily outside a major city or industrial area. I expect today you would find a chrome plating workshop in Davao City or perhaps Zamboanga, but going back to the 1970s or earlier I'm not sure. If you have a biker friend he might be able to tell you.
The form of the blade is one of the traditional fat-belly bolo shapes used by the Bagobo, and I think the shape goes back well over a hundred years and into the 19th C. As you note, it has a "distinguished" hilt with a decorative metal ferrule and a characteristic pommel with chains for hawk bells and perhaps a tiger bell, all of which indicate Bagobo
datu status. The white metal could be aluminum (of WWII or later vintage), tin from biscuit containers or other similar sources, or various alloys of nickel, zinc and copper (white brass, a.k.a. nickel silver or German silver, is 60:20:20 of copper:nickel:zinc). I have found tin strips on the scabbards of both Bagobo and T'boli swords. These tribes are resourceful and waste nothing.
As to age, that's really hard to judge. The blade could be antique, but I think the scabbard and hilt may be WWII era, perhaps a little earlier or later. You know the piece was in its present form in the 1970s, so the ensemble predates then.