A retained cud is created when a die piece breaks but doesn't fall away and keeps pressing coins. This example is on a 1940 S Wheat Cent's right wheat ear. Listed in "The Cud Book" by Thurman & Margolis as LC-40S-32R-Ret. Coin retains much mint red with some streaking and a fingerprint. Fourth photo show another die break on the reverse at K11 through the L in EPLURIBUS.