How do I remove stain from a silver quarter

[RBowtie97]

Hello! I sent a 1937 D quarter off to NGC thinking that it had mild toning. When it came back, it had a grade of "Uncirculated Details Stained". I broke the coin out and I tried dipping it in EZ Zest coin cleaner which removes toning but, nothing came off. Is there any way to remove the staining without hurting the coin? Any advice would be greatly appreciated! Thanks!

 

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[Jason in Enid]

If its valuable enough to be graded and slabbed, its too valuable to be messing with. Anything you do will devalue it further.