All the Stevens factory guns made from 1948 till the passage of the Gun Control Act (requiring serial numbers) had a date code roughly stamped on the center bottom of the action either just in front of the trigger guard or just behind the hinge. The stamp is a letter for the year and a number for the month of manufacture, stamped inside of a circle or oval. "A" represents 1948 and each succeeding alphabet letter represents the next year. "O" and "Q" were not used.
I don't know what the letter codes on the action flats mean. The 311A is a model number; there were several letters used with the number 311 to identify the various small changes in the gun over the many years of production...Geo
