Cutting and pasting from this website:
https://www.mdshooters.com/threads/dating-winchester-western-ammo-boxes.178198/The lot number will have a letter-letter-number or letter-letter-number-number series that indicated the date.
The first letter indicates the year, the second letter the month.
If followed by a single digit, that equates to a single digit day; if followed by two digits, the numbers are reversed to equate with a two digit day or dingle digit day with a leading zero.
Additional numbers and/or letters equate to production lines, operator or inspector numbers.
Years: To repeat every 20 years using our 26-letter alphabet, six letters were skipped: A, I, J, O, Q, and Z.
B 1928 1948 1968 1988 2008
C 1929 1949 1969 1989 2009
D 1930 1950 1970 1990 2010
E 1931 1951 1971 1991 2011
F 1932 1952 1972 1992 2012
G 1933 1953 1973 1993 2013
H 1934 1954 1974 1994 2014
K 1935 1955 1975 1995 (2015)
L 1936 1956 1976 1996 (2016)
M 1937 1957 1977 1997 (2017)
N 1938 1958 1978 1998 (2018)
P 1939 1959 1979 1999 (2019)
R 1940 1960 1980 2000
S 1941 1961 1981 2001
T 1942 1962 1982 2002
U 1943 1963 1983 2003
V 1944 1964 1984 2004
W 1945 1965 1985 2005
X 1946 1966 1986 2006
Y 1947 1967 1987 2007
Months: I and J are skipped
A - January
B - February
C - March
D - April
E - May
F - June
G - July
H - August
K - September
L - October
M - November
N - December
DH01 on the flap would indicate August 10, 1970.
Not sure if this is accurate, but it seems to confirm the '70 on the price tag.