Gold doesn't tarnish either. I guess if you have a gold bead up front you can use a gold vertical line, if a white or silver bead you can use platinum. But what if the sight is gold and the popup night bead is white? Problems, problems.

The best rear sight I can recall is on a Gye and Moncrieff black powder hammer .360 I saw decades ago at Abercrombie & Fitch and again a few months back at a CT dealer, no shallow V, just a flat leaf maybe 2" wide across both barrels with a big white enamel triangle, point up, under the center. Big fixed white enamel bead up front. This is one lovely little rifle.