Ben, usually the barrel gleams because some wag has taken a wire brush to it, often a POWER wire brush. Or sanding paper. Great for removing rust and everything else - like the engraving! Note that on the gun pictured the rear sight appears to either have been taken out, or replaced - but reversed when put in its dovetail. The longer leaf should be to the front, otherwise it tends to fall forward while you walk about with the muzzle down in usual fashion, and you end up shooting with the wrong sight - right over your target.
I'm with Daryl, would love to have that gun.
Aloha, Ka'imiloa