Has anyone else seen issues with older Leupold scopes discoloring? I've got this vintage Leupold Vari-X II 2-7x mounted on a Whitworth Express 375 H&H; and over a period of years, it has changed to what could be described as a "rose gold" color. The scope still works fine, and appears to be only cosmetic; so I'm just curious as to what causes this to happen. The gun has been stored in virtually the same climate- and humidity-controlled environment for the past 20+ years.