Best left to a professional. Find a gunsmith
Check the receiver and barrel.
Check the barrel and receiver. Sn's were not required before 1968
Under $100.
between the stock and the barrel
I believe that is a model 311. I have the same double barrel.
Manufactured between 1886 and 1916.
The Stevens double barrel shotgun is worth $350 to $450 dollars. The value is determined by the gun's mechanical condition.
Check the barrel and receiver
The Stevens model 311 was discontinued in the year 1989.You would have to contact Savage/Stevens to get the actual age of your double barrel shotgun.
wood
Try the receiver, barrel, forend
Check the receiver and barrel