Article by Diane James (from Diane Allmen Dexter Press collection) As of 09/2021.
AGEING OF DEXTER PRESS POSTCARDS: Being the owner of over 1,000,000 Dexter Press postcards I began documenting the publishing dates of these collectible cards. Below is a chart of how to date most Dexter Press postcards. Look for the Dexter press # on the back in lower left corner or upper right corner near stamp box. Some 1950s cards may have the # in the lower center of back.
1950-1951 #00001-39999 with no letter following
1951 #40000-59999
1952-53 #60000s
1954 #70000s
1955 #80000s
1956-57 #90000s
1957 5 digit # with -A following
1958 #1-10000-Bs
1959 #20000-Bs
1960 #30000-Bs
1961 #40000-Bs
1962 #50000-Bs
1963 #60000-Bs
1964 #70000-B to 99999-Bs
1965 #0-C to 9999-C
1966 #10000-c's
1967 #20000-c's
1968 #30000-c's to 49999-C(still looking for more data)
1969 #50000-c's
1970 #60000-c's
1971 #70000-C
1972-73 #80000-c to 99999-C's
1974 #1-10000-D
1975 #20000-D
1976 #30000-D
1977 #40000-D
1978-81 #50000-70000-d
1982-83 #80000-99999-d
Have Found -E cards not sure on dates yet
Do not have all the detail on the -D or -E cards just general time frame.