i just bought a stevens 5100 in 16 ga. side by side.
on the left side of the reciver it says
STEVENS
savage arms corporation
chicopee falls,mass,usa with a dog pointing to towards the muzzle just like this
top of left barrel proof tested 16 gauge 2 3/4 inch chamber
top right barrel selected forged steel
right side of the reciver 5100 in real small numbers
and on the bottom of teh reciver at the hing it has a shape that looks like a spade or arroww
it has 2 small silver beeds for sights
the pistol grip is chercked along with the under side of the fore arm. it has a 1/2 recoil pad
i have spent 3 days looking around on here and the WWW and cant find anything. other than it was made sometime form 30's-late 50's
You might check the underneath side of shotgun for a date code. If it has one it should have a number and letter in a small circle, the letter reflects manufacture date from 1949 to 1970.
Stevens Date Codes
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
X 1970 ?
(2007 Catalog of Firearms)
No date Code or serial number, likely pre 1948.
My understanding is that it is the predecessor of the Stevens model 311, so a good chance it won't have a date code.
stevens 5100 
