FWIW, I think the rear sight has been changed. Although they most all looked the same, dimensions, even screw holes, were sometimes slightly different. Even if the screw is tightened, it still looks too long to me. The curve in the sight base is because the sight base acts as it's own spring for elevation. If the sight base were straight, you'd have no tension, and little proper elevation adjustment. I had a few N-Frame guns, including 29-2s. The standard 29-2s came with the red ramp front and white outline rear sight blade. Your rear sight has a black blade. Not a thing wrong with that, in fact I prefer a plain black blade. But I think a previous owner likely changed some things on your gun to his/her preference.....

Reference the S&W Performance Center, I don't think it actually exists in the same form as when it did it's best work. They do LASER engrave the PC logo on all manner of guns now days, and perhaps they could do a competent job of rebluing your revolver. I admit I'm a bit dubious....

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NRA Life, COTEP 640