Check the stamping in the barrel. The chambering will be stamped into the barrel along with the Winchester Logo, the model number and the choke. If the gun doesn't say 3" or "magnum load" shells on it, It was made before there was such a thing as 3" shells. It's chambered for the 2 1/2 inch shell. (A 2 3/4" shell actually only measures 2 1/2", that extra 1/4 inch is the length of the crimp when it's folded out. 2 3/4 and 2 1/2 are the same shell)
You need a manual. Contact Winchester or find a gunsmith and ask for help.
I have one that I would sell.
I can say that the Winchester model 1200 shotgun was produced during the years 1964-1981.You might find Winchester,s home page and see if your shotgun can be dated by your serial number?
under the receiver in front of the lever.
Sears model 200 is Winchester 1200 try your local gunshop.
Check the receiver and barrels.
To find the year that any Winchester gun was made, you just need to know which model it is and what the serial number is (the model number and serial number are stamped on the gun itself). . Then go to this website and it will tell you when it was made: http://oldguns.net/sn_php/winmods.htm I'm trying to do the same thing, find the year of my model 1200 12 ga. Winchester magnum. I've used the oldguns site to get the year on 2 other winchesters but they don't seem to have the model 1200's on that site. I guess maybe model 1200's are not old enuf for oldguns.net :(
e-gunparts.com or Jack First in Rapid City SDAnsweron a Winchester model 1200
check the barrel and receiver.
Check the frame, receiver and barrel
Stamped on the receiver and probably the barrels, too.
Made from 1964 to 1981, no further sn breakdown I can find.