I take it you are saying that your coin lacks luster. This could have happened in many ways. Anything from being in the bottom of a lake to the bottom of a cup holder. Suffice to say nothing that happened at the mint would be the culprit.
That's about all though it has gotten you excited about finding something more , which is of great value ! Here is a link to a fantastic site on error coins to study and enjoy . http://www.error-ref.com/
The coin may have just been face down in whatever removed the lusted and not immersed. Side note , when you say flat we take it as there are no features or details left as if you sanded them away . Not the best description of loss of shine in this context.
Your description planted a different idea in my mind than what your photo shows. Your coin was struck with a grease filled die. The devices on a die are incuse and sometimes get filled with grease and grime causing those devices to not strike up on the coin like they are supposed to. Sorry, but your coin is very common and has no value over face. Keep looking. There are gems out there still to be found.
I disagree. All I see is a dirty grimy Quarter. The letters in AMERICA looks like crud. Especially Washingtons dirty appearance.
