They're listed here: (https://store.intellaliftparts.com/blog/linde-forklift-maintenance-kits/)

And below in case that page fails:

Year Linde Code
1990 A
1991 B
1992 C
1993 D
1994 E
1995 F
1996 G
1997 H
1998 I
1999 K
2000 L
2001 M
2002 B
2003 P
2004 R
2005 S
2006 T
2007 U
2008 W
2009 Z
2010 A
2011 B
2012 C
2013 D
2014 E
2015 F
2016 G
2017 H
2018 I
2019 K

ok, thanks that helps a bit but how do I find what letters represent what year?

It is the letter after the series in the serial #. On most sit down trucks the series start with a 3. For example, the serial # could be 324C..... the seres is 324 and C signifies the year. Another example is H2X393U... where the series is 393 and the year is signified by the U.