The best that I can do is state that the model 85 thru model 89 were made from 1912-1942,with total production being 38,500 guns.
The Savage/Stevens no 521 was made between 1930-1932.
The Stevens/Savage model 987 was made from 1972-1989.
The savage/stevens model 59 was made between the years 1938-1945.
The savage/stevens model 73 was made during the years 1964-1969.
I can say that the Stevens model 311 has not been produced since 1989.
Stevens was bought by Savage in 1920. Check with Savage customer service thru their website.
The savage/stevens model 94 was made by savage arms company during the years 1926-1945.There was a total production of 934,000 made.
The savage/stevens model 58 was made during the years 1933-1945.
the Stevens model 325 series was produced by Savage from 1947 until it was discontinued in 1950.Later savage manufactured the 340 (essentially the same gun) under the Savage name.Serial numbers were required under the gun control act which was made into law in 1968.From that point on all firearms made were required to have serial numbers.
the savage Stevens no 311 was made between 1926-1945 with 145,500 units made.
The Stevens Model 39A was produced between 1939 - 1947.
Your stevens model 9478 was made by savage/stevens between the years 1978-1985.