Definition:  Most retained cuds (retained marginal die breaks) sink in below the plane of the face.  On rare occasions the die fragment will protrude above the plane of the die face.  Any coin the die strikes will show a corresponding area of design that is recessed relative to the rest of the design.

This 1998-P quarter dollar was struck by a heavily damaged pair of dies.  The obverse face displays a dumbbell-shaped, rim-to-rim cud and, below that, a retained cud that encompasses the last two digits of the date.  This retained cud shows spectacular lateral spread and horizontal offset.  Unlike nearly all retained cuds, it is also recessed.  The retained cud that generated this island of design clearly projected beyond the plane of the die face.  It’s possible that a piece of die shrapnel or a piece of foreign matter lodged in the gap between die fragment and die neck, causing the die fragment to protrude.