I purchased a used B+W 72mm circular polarizing MRC filter from B&H, and used it for a month. I was cleaning it yesterday, with all my lenses and camera, next to a window with bright sunlight. And I noticed, when holding it at a certain angle, these lines appeared. They appear to be *in* the glass, as there are no physical marks on the surface. And I only see them at certain angles to the light. I haven't noticed any image quality issues, but I haven't looked for it yet either. Has anyone seen this before? Know what it is?
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