Contact Customer Service for Savage Firearms. They have owned the Stevens name since the 1920's.
I had to buy a gun to break. Don't have it now. I do have a parts list from Stevens i.e. exploded diagram. Not much use unless you can source a second hand gun or part.
This would be a Stevens single shot worth up to $75.
5-50m depending on load
It probably doesn't have one. Serialization of long arms was not required before 1968 and few manufacturers of utility-grade shotguns used them.
There is no "break in" shotgun. A "break open" shotgun is a single barrel, double barrel, or combination rifle/shotgun which breaks open in the sense that a lever will unlock the action, allowing the barrel to pivot at a hinge at the front of the receiver, pivoting the rear of the barrel up to expose the chamber. A shells may be loaded into the chamber and the barrel pivoted back to close the action. The act to "break in" a shotgun means to fire it a few times to loosen it up.
If the vendor code starts with 101 it was made by savage arms a model 94 Stevens shotgun common as dirt but a good old gun
A custom fit Purdey double shotgun
Break open.
1900's to 1990's
Google.
70-100 years.
Contact the maker.