As someone who lives in the Denver metropolitan area, along with more than three million other people, I can assure you we have our share of pollution and such, and right now some very hot weather. I have not been to the mint here in nearly forty years, but I have noticed that the coins I collect are sharper and brighter if they come from Denver versus Philadelphia. But then being at ground zero, 20 miles from the mint, I should expect that.
I would also agree with that. I mean, even if taking into account where you live and how far the Philadelphia coins had to travel it seems like they put them in the bag and throw them around or something rattle them up without care.