“Stains” on my YG Yacht-Master I

[kenm]

One of my favorites is a yellow gold Yacht-Master I that I bought pre-owned in 2016. It’s always had these “stains” on the band just above and below the bezel, between the polished and brushed links. I paid a great price for the watch, so I didn’t fuss too much about the condition. It’s really in great shape except for the stains. When I rub with a soft wet cloth, the stains don’t change. I’m thinking of using a metal cleaner (not polish), but not sure which would be best, or if any might damage the gold alloy.

Has anyone seen these types of stains? Has Rolex ever had issues with the 18 karat gold alloys that they use, where maybe copper leaches out?

Thanks in advance for your thoughts! There’s so much Rolex knowledge on this forum :) Ken