Hermès has been debossing their leather goods since 1945. Typically, larger items have a combination of a letter and a geometric shape (either a circle or a square). This represents the year it was manufactured. Hermès bags made prior to 1970 will have no shape - just a debossed letter. 
 

No Shape

Circle

Square

1945 A

1971 A

1997 A

1946 B

1972 B

1998 B

1947 C

1973 C

1999 C

1948 D

1974 D

2000 D

1949 E

1975 E

2001 E

1950 F

1976 F

2002 F

1951 G

1977 G

2003 G

1952 H

1978 H

2004 H

1953 I

1979 I

2005 I

1954 J

1980 J

2006 J

1955 K

1981 K

2007 K

1956 L

1982 L

2008 L

1957 M

1983 M

2009 M

1958 N

1984 N

2010 N

1959 O

1985 O

2011 O

1960 P

1986 P

2012 P

1961 Q

1987 Q

2013 Q

1962 R

1988 R

2014 R

1963 S

1989 S

 

1964 T

1990 T

 

1965 U

1991 U

 

1966 V

1992 V

 

1967 W

1993 W

 

1968 X

1994 X

 

1969 Y

1995 Y

 

1970 Z

1996 Z