The crack will be easy to fix if you take the scales off and apart.
What I would use for the repair is some Good epoxy, then sand the scales with 400grit wet or dry paper-DRY so you can collect the clean sanding dust to mix with epoxy to fill the crack, but first you must clean the black from the crack, an needle point or fine knife point will scrape that out, then mix epoxy and bone dust and fill it in, then sand when dry and polish going to finer grits and buffing.
Done carefully you should not see the crack at all.