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Lincoln Cent Retained CUD
A Cud is a die break that connects rim to rim and is only called a cud because it looks like a wad of cud in shape. So there's no such thing as a cud mint error, it's just a name applied to this particular type of die break.
Most of the dies breaks form a half circle as the break only occurs on the rim or edge of the die's design. When this piece breaks out then the planchet metal is squeezed into this cavity, forming the cud shape.
If however the die break does not break out then it's referred to as a retained cud or die break and you will see the die crack starting at one point of the rim then "circling" back to another part of the rim. Unusually these die breaks are deep and the crack looks thick and jagged when in the retained state.