We've got a batch of seconds again!
What a great way to get some perfectly usable disks that just have some comestic problems for an amazingly low price.
Sometimes in our plating process we don't get an appropriate diamond dipersion on the disk. When that happens we get small spots that do not have any diamond coverage. This won't affect grinding at all but it looks a little funny.
We try to clear these babies out of our inventory about twice a year.