, You may be referring to a linear plating blister/bubble and or DDD (die deteriorating doubling) You can use the "search box" upper left on the screen to see examples of both terms..good luck on future finds
Depending on the crack size. If minor, no premium. If all across the full face of the die, then there would be a premium. But images will tell us more. Most die cracks don't carry a premium, but some do when the are large.