I don't have a picture right now (the coin is currently in my dorm room), but the most impaired proof I've ever found was a 1980s nickel. The only reason I could tell it was a proof was due to the S mint mark on the coin. What was the most impaired proof you've ever seen?
Any pictures? I saw an image of a proof Trade dollar that would grade fine. I cannot remember if it was graded or not, but it was circulated so heavily that you would need to be familiar with the proof diagnostics to recognize it.
I think there have been threads about this in the past, but I don't have time to search right now. If I'm remembering correctly, someone linked to a PF03 or PF04 coin.
I suppose there's no reason you couldn't wear down, say, a Stella until it's a featureless disc -- nothing else was made in that size and composition but a Stella, and they were only made as proofs, so it would necessarily be a PF01. That might also be an unassailable record-holder for any "lowball" competition. All the same, I hope nobody sacrifices a Stella for that purpose.
No, it's a proof, I shot those images in a dark room, no lights on the scope with a hand held LCD trouble light ..
I found a couple of proof quarters back when I was in high school working at subway. Also found my oldest circulation find in that change drawer. A 1902 barber dime.
I've found a few impaired Kennedy proofs in rolls, but I got this back from a U-Scan at my local grocery: