You can try looking for a 'date code' stamped in the metal,,usually the receiver/action. Denotes year of manufacture. Was used by Savage/Stevens/Fox Company 1949 till just after the GCA/68.
A single letter usually in a circle. Sometimes a number will accompany the letter,,sometimes there will be no circle around it/them. It varied alot over the years in use.
I don't know what the accompaning number (if there) denotes (month perhaps?).
Some sources state these codes were only used on double barrel shotguns,,others state used on single shot shotguns in addition.
I've seen them on Savage 99 rifles,,so I believe they were used on all their products wether they required a serial number at that time or not.
Shotguns and cal22rf long-guns were not required to be serial numbered prior to GCA'68. All other firearms were. Those 2 catagorys were added in the '68 law.
A 1949 B 1950 C 1951 D 1952 E 1953 F 1954 G 1955
H 1956 I 1957
J 1958 K 1959 L 1960 M 1961 N 1962 P 1963 R 1964
S 1965 T 1966
U 1967 V 1968 W 1969 X1970
No letter 'O' or 'Q' used in the sequence.