I saw an old one from around '49 w/Tentite stocks and it was a blackish blue.
If the wood was blond it's birch from mid 60s, I believe, to the end in '88.
Except for the couple of years w/brittle plastic they were walnut.
Some of the birch had walnut stain. I could be confusing the walnut w/Fox B as it was the higher grade "311" and had walnut.
Savage/Stevens/Fox B was at the factory in Chicopee Falls from the end of WW-II thru 1960. By 1961 they moved to their new factory and offices at Westfield, Mass.
That might give you a clue to the age.
Also, I read where the 3" mag was proofed in 1954, but I'm not sure when the 3" was added to the Stevens 311.
It was there by the 60s for sure. Someone will come along that knows more.
Good luck...
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I looked again at the old 311 and it was a case colored receiver. The barrels were dark/blue.