It's the result of Deteriorated Die | Die Deterioration Doubling, when the die met or exceeded its useful life stage.
It looks like doubling but this is not the case. It is also different from the category of die chips because the cause is the extreme metal fatigue of the die.
Generally, in any deterioration of a die, the effects of fatigue are beginning to be seen on the letters or numbers and extend by to the center where the drawings are.
It's also possible that this deterioration can reach, depending on metal fatigue, the field of the die to create what is known as an orange peel effect.