Found it -
http://rib.net/forum/showthread.php?t=27800&page=2
1980 - S 1990 - D 2000 - T
1981 - R 1991 - C 2001 - S
1982 - Q 1992 - B 2002 - R
1973 - Z 1983 - P 1993 - A 2003 - Q
1974 - Y 1984 - N 1994 - Z 2004 - P
1975 - X 1985 - K 1995 - Y 2005 - N
1976 - W 1986 - J 1996 - X
1977 - V 1987 - H 1997 - W
1978 - U 1988 - G 1998 - V
1979 - T 1989 - F 1999 - U
So 'S' is either a 1980 or 2001 ?