Post mint staining. It's impossible to know how it happened. BTW, it's a National Parks/America The Beautiful Quarter, not a State Quarter. The State Quarter program ended in 2009.
Thank you. I'm assuming face value then for, a post mint staining. Have these "stainings" occurred in/at the mint? If so what are they referred to as and do they hold an increased monetary value? Thanks
They don't come from the mint in that condition and they will never be worth more than face value (unless the stain looks like the virgin Mary).
If you're hoping to find coins worth additional premiums beyond face, learning is the key to success, and even then there's little else that offers a worse return on your time investment. If you're going to search coins for varieties or errors, it really should be done only because you have a passion; at least that way, if you do find anything worthwhile, it's all gravy.