Flaking as used by Winchester and Colt and S&W collectors refers to the blue simply peeling or flaking off like an old paint job. In those guns it happens on a Carbonia blue that is a heat process of bluing. Lugers normally were rust blued or dip blued and those types do not flake. The area below the hammer of the Winchester pictured is classic flaking. The receiver is totally flaked everywhere else! Incredibly the metal remains smooth as glass to the touch.
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