[ithacaartist]

The straw color is developed on the top molecules of the piece. Abrasion from handling and probably discoloration from skin oils or whatever wears away the color on the most exposed portions of the parts. Remember, they're still in the white because they don't have the "pre-rusted" protected qualities of the main finish. It makes perfect sense that the toggle lock retains the most straw color because it is submerged within the toggle knob.

The milled areas for indication of "safe" would certainly be susceptible to oxidation and all but the most carefully oiled and stored can't avoid taking on a touch of oxidation/color. It might be possible to detect in-hand a re-do by the difference between an area that has been polished to restore the raw surface there and one that has not (characteristic tool marks, etc.).