These pins are "seconds," meaning they have flaws or imperfections (such as bubbles, scratches, or discolorations in the enamel) that prevent them from being sold at full price. They're still very wearable, and many of the imperfections are only noticeable on close inspection. If you're looking for something pristine, these aren't your guys; but if you're interested in snagging a misfit pin at a discounted price, you're in the right place.
B grade pins have minor flaws of the kind that are mostly unnoticeable unless someone is all up in your grill closely inspecting your pin.
C grade pins have more serious flaws (or a larger number of minor flaws). Think of them as the sort of roughed-up punk rock versions of the design. They're still totally lovable, but they're definitely imperfect and are discounted accordingly.
Note that these flaws are not represented in the photos.
All seconds are sold as-is and are not eligible for returns or refunds.