The 'date code' was used on Savage made firearms in those yrs. Includes Stevens and 'Fox' brand guns as Savage owned both at the time.
Before 1968, shotguns were not required to be ser#'d under Fed law, and Savage usually did not do so. They did stamp these date codes on the shotguns (and just about every other firearm including the Model 99).
On the SxS like the 311, it's usually in an oval or circle on the bottom of the frame near the front nose where the forend fits. But you're likely to find it stamped most anywhere on the action. Sometimes there is one or two numbers along with the letter inside the oval/circle, different opinions on what the number(s) stands for.
After Dec '68, Fed law (GCA'68) required a ser# on shotguns and 22rf long guns, but the date codes continued to be struck along with them intermittently for a couple years by Savage/Stevens/Fox.
Savage says there are no records available if you ask them to search.
It's the old 'we had this fire and the sprinklers ruined all the records refrain."
The Models going back farther than the date code (1949) are just a mystery as far as exact date of mfg.
Some can give an educated guess at it by looking at mfg features, finishes & styles.
Model 311's made starting in 1968 that were ser#'d started with letter prefix 'A' and 000001. A six digit ser# was used from the start in '68 I believe.
They ran the production ser#'s up to A999999,,then started over with
B000001.
They continued like that producing 1 million guns under each Letter prefix.(Model 311's, 311 model variants, and 311 'store brand' marked guns)
They used letter prefix A thru E. The highest (last) ser# was approx E958xxx. I'm sure you can find the exact info somewhere on the net.
The prefixes were run till they reached 999999, without regard to any specific date, end of year, turn over date,ect.
So the Prefix can't be used to tell production data .
Don't confuse the ser# letter prefix (A thu E) with the Model 311 Series letter designation 311A thru 311H. These latter Model designations denote mfg, cosmetic and material changes done to the gun while in production.
One more confusing number to add to the 311 ser#. In the late 70's sometime, the factory started stamping a 1 thru 20 in front of the ser# on each gun of like model & spec.
I've read this was for shipping purposes. To make ID easy so that the standard shipping container of 20 guns could be easily packed with 20 of the same spec guns.
I don't know if I buy that or not. I think it may have more to do with ser# demands of BATF .
But that's what's out there!