Platoon Commander

I recently bought a Stevens Model 311 Series H, 12 ga double. It's a pretty plain-Jane shotgun with minimal checkering on the fore end and grip a plain barrel rib and one bead sight, but is very clean and I only gave $250 for it. Chambered for 2-3/4 and 3' shells, modified and full chokes (I think), twin triggers and 28' barrels. Stevens discontinued the model in mid to late '80s, and they didn't have serial numbers before 1968, but I'd like to figure out when mine was manufactured. The SN# is C387493. Anybody know of a reference source that would show manufacture dates?
I once had a Fox Model B, a similar shotgun to the 311, but a little fancier, and it was modified and full choke, which is why I think this one is also. I'm going to take it to a local shop and have them gauge the barrels to see for sure. I've wanted another side-by-side ever since I sold the Fox B, I still regret selling it. I also wanted a shotgun I could shoot skeet and trap with, my Mossberg 500 only has an 18' barrel; it would have cost me almost as much to buy a longer barrel for the Mossberg as I paid for the Stevens.