The
Lincoln Cent design has changed a lot over the years, new dies, more detail.
Take a look at some cents from the 1960's and compare them to cents from today, the difference is easy to see.
Sometimes a reverse design from the previous year, or even the year to come, can get used with a current year's obverse die. These are known as transitional errors. Some examples include the 1988 cent with the reverse of 1989, 1992 close "AM" in AMERICA, and the wide "AM" on some 1998-2000 cents.
Sometimes a die meant for proof only issues gets used for business strikes. There are many transitional error to be on the lookout for.