Lee, that's a good suggestion. I'm not enough of a chemist to fully understand what I mean when I say "salts," so I just parrot what I have read or heard elsewhere. I do know that when I got the front sight block separated from this barrel it was all red rust down in the pocket, but superficial. I cleaned it out, brushed clean the sides of the tenon on the sight block, dried all, oiled all, and put it back together.
The only other gun in my collection that shows even a hint of of trouble at the sight base/rib interface is also a high polish mid-'50s revolver. My satin finish revolvers do not show this problem, nor do I recall seeing photos of satin finish revolvers with this problem.
Maybe it's just limited personal experience, but does this problem show up on K frames too? I have run into it only on N frames, but then my '50s-era Masterpieces are all satin guns.