The Model 58 was manufactured from 1933 to 1945, but I don't know if all three gauges were available from the start of production or if some were added later.
Your Stevens model 30 was made from 1933-1934.
1964
The Stevens/Savage model 987 was made from 1972-1989.
1900
The stevens model 77 slide action shotgun was made from 1955-1971.
your Stevens model 15-A was made from 1936-1945 with 224,000 being made.
The savage/stevens model 73 was made during the years 1964-1969.
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.
The best that I can do is state that the Stevens model 311 side by side was discontinued in the year 1989.
I can say that the Stevens model 67 was discontinued in the year 1989.
The original Savage?Stevens model 311 shotguns were made from 1926-1945.The more recent made Stevens model 311 shotguns were discontinued in the year 1989.
The Stevens model 15 was made from 1936-1971.