you definatly got something going on there that could be error. I'll let the experts chime in though as errors not my speciality
I can’t say from those photos, they’re far too blurry and not close enough. I’d guess vice job. Probably pressed between 2 coins in a vice based on there being curves on both sides.
Your photo is a little blurred, but I'd say another coin laid on top of it, leaving the mark. Have you tried: a acetone rinse? Using a soft wooden toothpick to determine it the mark is raised or incused? No error in my opinion, but what do I know?
I’m with Mountain Man, another coin was laid on top of this quarter and a stain was created. Judging from the line I’d say it was another quarter.
First, let me say, I know nothing! And I mean that. I'm not an "error" expert, just have made many "errors" in my life. But, the thing that makes me wonder about this one is this: the two arcs are opposing each other. I don't see how that could be? To me, they would need to be oriented in the same direction. Again, in case you missed it the first time, I know nothing! Keep trying, keep posting, keep hoping, well, just keep on!
Both the Obv and Rev show a ring. Hey @Mountain girl put your phone on something stabile then try to take a clear photo. Could be a stain, toning, or just damage.
If the mark was organic, the acetone could dissolve it, not so if it is an alteration in/on the metal. Jim
As @desertgem posted, it could remove the mark if it is a stain. Acetone is one of the chemicals that shouldn't hurt a coin. It dissolves stains, spills, environmental staining, all without doing any damage, or most importantly, hurting the value of the coin. Find some coins that have "gunk" on them and try it as an experiment.
I place my phone on a glass or a pint jar so that it's steady, then snap the picture. Generally works well for me. Getting the light just right is the trick!
