1944 d/s omm 1
1944 d/s omm 2
1946 s/d omm 1
1951 d/s omm 1
1951 d/s omm 2
1952 d/s omm 1
1956 d/s omm 1 wdmm 1 (dual mintmark)
1956 d/d/s omm 2
Over Mintmarks (OMM's)
The above list represents the most commonly accepted over mintmarks
(OMM's) in the Lincoln Cent Series.  It may seem strange to you that the mint
would change its mind after punching a mintmark, especially if you think that
the S mintmark is punched at the San Fransisco Mint and the D mintmark is
punched at the Denver mint.  The truth is that both the S and D mintmarks are
punched at the Philadelphia mint where all dies are prepared.  So a mint
employee could easily change a D to an S for a variety of reasons before the
dies are shipped to their respective mints.  

What about the
1980 D/S cent?    
The 1980 D/S omm 1 was debunked in 2006.   
Die Variety News had an article
proving that what looked like an S was actually die gouges in the field.  The
article was Vol. No 2. July/Aug 2006 written by Billy Crawford.   Also, ANACS no
longer certifies this variety.  Some collectors and dealers are not aware of
this.  Investing in this variety is not recommened.  

The following is a list of
possible OMM's:
1911 D/S omm 1