Well, the top one should have been made after 1952 but before 1967, while the bottom one could well be as late as the one I posted above. H&R's are generally pretty easy to date as the letter(s) serial number prefix advanced alphabetically (albeit with some gaps) each year. Here's the rundown -
A 1940
B 1941
C 1942
D 1943 *
E 1944
F 1945
G 1946
H 1947
I 1948
J 1949
K 1950
L 1951
M 1952
N 1953
P 1954
R 1955 **
S 1956 ***
T 1957
U 1958 ****
V 1959
W 1960
X 1961
Y 1962
Z 1963
AA 1964
AB 1965
AC 1966
AD 1967
AE 1968
AF 1969
AG 1970
AH 1971
AJ 1972
AL 1973
AM 1974
AN 1975
AP 1976
AR 1977
AS 1978
AT 1979
AU 1980
AX 1981
AY 1982
AZ 1983
BA 1984
BB 1985
BC 1986
* For some 1930's Sportsmans a "D" serial number prefix did not denote year of manufacture but rather "double action".
** An "R" serial number prefix will also be found on the circa 1940 Model 196 Eureka Sportsman.
*** For some 1930's Sportsmans an "S" serial number prefix did not denote year of manufacture but rather "single action".
**** A "U" serial number prefix will also be found on the circa 1938-39 Model 777 Ultra Sportsman.
In 1981 H&R offered a special, engraved version of the 999 to commemorate their 110th anniversary. These "1 of 999" revolvers were numbered from 999001 to 999999.
After Harrington & Richardson proper had ceased operations, manufacture of 999's continued under the aegis of New England Firearms (H&R 1871) utilizing a new series of serial number prefixes -
HA 1987
HB 1988
HC 1989
HD 1990
HE 1991
HF 1992
HG 1993
HH 1994
HJ 1995
HK 1996
HL 1997
HM 1998
HN 1999
Additional notes on 1930's era Sportsman serial numbers -
Since H&R's records from this period aren't extant, an accounting of serial numbers can only be based on observation and to some degree conjecture.
It may be that prototype and pre-production samples were numbered beginning with 1 (or 01), while regular production started at 101. Low serial numbers have been documented up into the 1600 range. By the 3000 range, the "S" prefix (for "single action") had appeared, and by 4000, the "D" prefix (for "double action") was being applied. It isn't at all clear whether the single and double actions shared a serial number sequence with the "S" or "D" prefix being utilized as appropriate, or if each was numbered in separate sequences (so that there could theoretically exist two guns with the same serial number save for the preceding "D" or "S"). It seems certain that the Ultra Sportsman and Eureka Sportsman had their own serial number sequences (preceded by "U" and "R" respectively). In any case, at some point above the D28000 range (circa 1937), the "D" at least was dropped and serial numbering reverted to a straightforward all numeric progression that reached as high as perhaps 90000, ending there as the practice of sequential date code prefixes (starting with "A") with yearly recurring numbers was adopted in 1940.
