B-Grade pins are the pins that have determined to be not up to my normal standards of quality. When I get pins from my manufacturer I look at every single one of them to grade them, I set aside all of the B-Grades and keep them out of regular stock. They are then saved up to have a B-Grade Sale where I sell them at a discount. Because of this discount, B-Grades are a great option if you're going to put your pins on a back-pack, purse, or some other high abrasion area where they're likely to get scratched.
Examples of what might cause a pin to be deemed a B-Grade:
Dust in the enamel or a small smudge on the surface is the most common reason for a pin to be a B-Grade. Honestly, lots of times I'm the only one who notices these. On this Hedge Witch pin you can see the smudge in-between the crystal and the candle.
This is another really common imperfection, a slight dent or dip in the enamel. You can see it on this pin just above the right eye.
This happens more rarely, sometimes a pin is just missing a color of enamel all together. When this happens it's always a very small portion of the pin like in the example above. You can see that top row of stitches in the heart is missing the purple color that is supposed to be there.
Out of place color is a very rare occurrence on most pins. I do have a batch on these Home Sweet Home Pins where there is some extra blue color in the lavender. Other than that you're actually slightly lucky if you get one of these B-Grades as they really don't happen very much!