Wide AM and Close AM Varieties
Until 1992, both proof and business strike Lincoln cents were made using the same type of reverse die
all with a
Wide AM.  In 1992 the mint created a new reverse with a Close AM for that seems to be
intended for use starting with 1993 cents.  All 1993 cents, proof and business strikes, have a
Close
AM
reverse.   Beginning in 1994, the mint began using the old Wide AM reverse on all proof strikes
and the new
Close AM reverse on all business strikes.   In other words, instead of using the same
reverse on both proof and business strikes, the mint began using different reverses on cents dated
1994 and beyond.   If things went according to plan all proof cents dated 1994 and on would have the
Wide AM design, and all business strikes would have the Close AM design.   Naturally all 1959 - 1992
cents should have had
Wide AM designs on both proof and business strikes.   Well, mistakes must
have been made because several variations have appeared.   1992 and 1992 D business strike cents
have been found with
Close AM reverses.   1998, 1999, and 2000 business strike cents have been
found with
Wide AM reverses.  And, 1998 S and 1999 S proofs have been found with Close AM
reverses.   The following is a list according to rarity of all known abnormalities, the 1992
Close AM
being the scarcest.  This list does not include the other know transitional reverse varieties, such as the
1988 P & D RDV-006.  

1.  1992 Close AM - extremely rare
2.  
1992 D Close AM
3.  1998 S Close AM
4.  1999 S Close AM
5.  1999 Wide AM
6.  1998 Wide AM
7.  2000 Wide AM - least rare

Their are two good ways to distinguish the
Wide AM reverse from the Close AM reverse:

1)  Obviously, if there is a large space between the A and M in AMERICA you are looking at a "
Wide
AM
".  If it appears the A and M are practically touching, you are looking at a "Close AM".  Be aware
that there is still a space on "Close AM'' cents.  It is just a smaller space.  

2)  The Initials FG on the reverse are further from the memorial on the "
Close AM" reverse.  The
initials are a better diagnostic than the AM!

Remember that it is opposite:  A "
Close AM" has wide initials, and a "Wide AM" has close initials.
Don't just look at the space between the A and M.  As dies deteriorate, they spread.   The die may
spread far enough to create what appears to be a small space between the A and M.   Always look at
both the AM and the initials.  

Wide AM varieties are also referred to as "Type 2 Proof Reverse".  ANACS labels these coins "TYPE 2
REV "PROOF" HUB" on their slabs.  NGC and PCGS label them as "
Wide AM".  

If you want coins to compare, I suggest the following:
1993-1997 and 2001-2007 P and D cents should all have
Close AM reverses.
1959 - 1991 P and D cents should all have
Wide AM reverses.
1994 -1997 and 2000- 2007 S proof cents should all have
Wide AM reverses.
1993 S proof cents all have
Close AM proof reverses.  

I suggest that you check any 1998 S and 1999 S proof sets for
Close AM's.  If you find a Close AM,
then you just discovered something rare and valuable.  Furthermore, discovering something like a
2000 S
Close AM would be truly rare.