1976-S Bicentennial Quarter

there is no "Impairment" on the coin. this term is used when a proof coin makes it way into circulation and there are signs that it had. the most prominent marks that would indicate this is the right obv field scratches. you would not find that on a proof coin that was never circulated.

photographing proofs is not an easy task. glare from lighting can alter the surfaces and also create shadowing. however, there may be some MD going on although not very common proof coins

Proofs are struck in a controlled environment with high&-precision dies and planchets. However, even in this setting, minor mechanical issues can cause Machine Doubling.

Let's take a positive spin on the release into the wild: some proud American coin enthusiast is celebrating the 250th anniversary of Independence by sprinkling some neat vintage coins into circulation. I plan to do the same at our annual fall fest booth!

I would have said PR58 based on the obverse circulation evidence. But I fully admit that I don't even remember reading articles about grading proof coins found in circulation.

Even if it doesn't have significant value, it is still a beautiful coin

I agree, a very beautiful coin!