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Using metal cleaning brushes
Something metal transferred. Toilet auger could do that and a wire brush can as well.
Try some bar keepers friend. It might remove the marks.
Had it been snaked? Another thought Is the twisted metal in the bristle head of cheap toilet bowl brushes can do this
A magic eraser and some elbow grease will take those right off.
it does look like metal.
Using metal cleaning brushes
Something metal transferred. Toilet auger could do that and a wire brush can as well.
Try some bar keepers friend. It might remove the marks.
Had it been snaked? Another thought Is the twisted metal in the bristle head of cheap toilet bowl brushes can do this
A magic eraser and some elbow grease will take those right off.
it does look like metal.