According to a phone call to the Heritage plant, Heritage serial numbers
started with the letter ‘A’ in 1984, and have continued to advance by one
letter every year thereafter. So:
A 1984
B 1985
C 1986
D 1987
E 1988
F 1989
G 1990
H 1991
I 1992
J 1993
K 1994
L 1995
M 1996
N 1997
O 1998