Post Mint Damage (PMD):
PMD can unfortunately take on the characteristics of doubling as well as the appearance of an infinite number of imaginative Mint Errors.

When it comes to the appearance of doubling caused by hits to the surface of the coin, no where does this confuse new collectors more than when it happens to the ear. Coins take hits the instant after they are struck. Hits can come in the form of myriad ways and will often do what appears unlikely. New collectors are frequently bemused by depressions on the lower parts of Lincoln's lobe and confuse it with any number of known Doubled Dies that impacted the ear such as: 1984P DDO-001, 1997P DDO-001 and 2006P DDO-004. There are also a few minor doubled dies for 1984 with doubled lobes listed by Wexler and illustrated by Brian Allen in "...Pocket Change" that also haunt the minds of new collectors and further confuse them with damaged ear lobes.

As with all forms of doubling associated with Doubled Dies, the doubling ADDS to the size of the device effected, it does not take away from it. A hit on the ear causes the loss of some of the ear. The simplest way to tell is to check the exposed part of the ear and see if it is normal sized or smaller. If it is smaller, then it is not a Doubled Die and one has to ignore anything else. Below are two examples of a hit ear. Notice the extra hit marks around the ear (white arrows). Compare the hits to the illustrations of normal ears and one can see the missing area of the ear. For a similar comparison, see the last example which is MD on the ear (and hair). There too one finds a loss in size as opposed to an increase in size.

   
 
   
  Finally, below are actual examples of Doubled Dies that have doubled ears. They all happen to be class IV Doubled Dies. Notice how they all have a normal sized ear, plus an additional area of doubling that is rounded. In order: 1984P DDO-001 with an extreme spread SW, also visible on the tie and beard; 2006P DDO-004 also with a small portion of the lobe SW; 1997P DDO-001 spread south also visible in the hair details; & 1941P DDO-005 with a SW spread that also impacts the date and TY of LIBERTY.
   
 

Sometimes, for whatever reason, be it an accident or purposeful, coins are pressed into other coins. The result is an incuse, reversed image of the coin that made contact. These are erroneously called everything under the sun, such as: a Doubled Die; an [in collar] Double Struck Coin (though collectors/sellers omit the "in collar" part as they don't know); a Die Clash; a Counter-Clash; & a Dropped Letter error. Most often Double Struck and Dropped Letter are used.

Below the illustration shows a Lincoln that was pressed (but probably smashed) against another Lincoln cent resulting in the reverse incuse IN G (from IN GOD) across the lower bust (indicated with a black arrow). Here there are tell tale signs such the indention of the rim and stress fractures to the surface of the coin (white arrows). Below that is 1983P CLO-002, a Counter Clash, showing and extra shifted "IN", and below that is a 1972D with evidence of a die-clash in memorial bay 2 - an incuse Y from LIBERTY can be seen.

Illustrated below is a curious case of two stray hits on a 2009D FY TY that, believe it or not, mimics notches from Single-Squeeze hub-doubling. There are two, well placed dings on the NW corners of TY, they however are not rounded but sharp with a shine to the exposed area (that was hit). There is also no extra thickness or distortion which is typically present on modern DDOs. Below that is 2009P FY DDO-001 for contrat which exhibits pho
 
Images and text © Jason Cuvelier 2009: www.cuvelier.org