Well, 26 hour soak in Hydrogen Peroxide. To me, there is a very noticeable difference in color. I don't mind a little yellowing, to show age, so I stopped. I could have kept going, over the next couple of days, and really whitened it up, but I wasn't looking for the new bone look. Another observation was that the Peroxide did little to lighten the rust staining, but it did loosen it up, to where it just wiped off, inside the scales. A lot of the dark area that is now seen, in the pivot pin area is the dark area of the blade, beneath the scales. These bone scales are somewhat translucent. So, I will let Y'all be the judges. Before: After: I had to apply some Mineral Oil. The solution dried the scales out.
Looks great and still looks vintage in a good way! I'm glad you stayed away from the chlorine; I heard bad things regarding bone, like turning it to mush.
There's an 8-bit guy on Youtube (just forgot the whole name/etc) who does stuff with old music keyboards and old computers. He uses the peroxide that is used by hair dressers, but also uses sunlight. For something as small as the scales, you could do the following. Get a one gallon plastic bag, put peroxide in the bottom of the bag, put the scales above the peroxide in the bag, and set the whole thing in the sun. The peroxide generates ozone, which when combined with UV in sunlight, bleaches very quickly. Amazing results on an old Macintosh case.
I'll give that a try, next time. But, I don't have the hair dresser peroxide. I was pleasantly surprised how well the Over The Counter stuff worked.
The over the counter stuff will do the same - you're looking at a much smaller item than he does. I mean, he rubs it over an 88 key keyboard case