Girls and boys, I have a gold togo birkin with palladium hardware (I think it is, it is silver in colour) that is about 6-7 years old. I have noted recently that there are some black marks on the hardware. I tried to rub it off with tissue paper and I could only remove some of the marks but not all. The marks look like they are appearing from within...is this some kind of oxidisation? Anything I can do about this? Thank you so much in advance for your help.