Nice cud find! Is the third digit an '8'? If yes, how much does the coin weight? It looks like a copper cent, so if it is, it must be from 1980 or 1981 if I see an '8' in there.
That's what it is, A NICE BIG CUD ON A LINCOLN CENT...you didn't lie with the title. RETAINED CUD, IMHO
I disagree. That is a plain old cud. A retained cud (struck by a broken die where the broken piece has not completely fallen away) will have very faint features in the cud. The cud on the OP's cent is just a blob because that portion of the die broke and fell off. edit After a closer look you may be correct. It does appear the cud is flattened out but I don't see any hint of the numerals of the date.
I could see that CUD bringing $17-25 on ebay. It is a nice size. CUDs on dated cents usually command a little more of a premium.
A retained cud will show displacement of the die face that has separated, but it will retain all the design features of the die. It's a piece of the die that has broken away from the rest of the die, but has been "retained" in place. This is not a retained cud. http://www.coinworld.com/Articles/ViewArticle/retained-cud-diagnostics-sometimes-leave-room