Proofhoue.com will get you in the ballpark.
You will need to include the shotgun model number,or model name.Type of shotgun(single shot,pump action,double barrel,or semi-auto)along with the serial number that you have provided to get the correct age of your Winchester shotgun.
Try a 1300 barrel
Start with this site www.midwestgunworks.com
Check the receiver and barrel
I have no idea of what it is?Please describe the Winchester firearm with this serial number.Is it a rifle,shotgun?Is it a lever action,pump action,semi-auto,or bolt action?What caliber is it?what gauge is it(if a shotgun)?describe the barrel length.All this is required to get a answer to your question.
This cannot be answered without a more detailed description of your shotgun.Is your shotgun a semi-auto,over under,pump action,single shot?What markings are on your shotgun?What is the barrel length?
"Your" Winchester Model 21 Double Barrel Shotgun was manufactured in 1933, giving it an age of 77 years, as of 2010.
Your winchester model 1912 pump action shotgun which was produced in the year 1942 will bring between 350-600 dollars,depending on the amount of original finish remaining,and a good bore.The plain barrel model will bring less than a shotgun having a vent rib barrel,or a matte rib(solid rib) barrel.
A Winchester model 12 pump action shotgun in 70%-80% overall condition and made in the year 1937,will bring between 295-350 dollars.You may add 20%-40% if your shotgun has a solid matte rib barrel,and 50%-60% if your shotgun has a vent rib barrel on it to the above listed price.
Please include the model number of your Winchester shotgun to get a correct answer to your question along with the serial number.
Your Winchester model 1911SL(self Loading)shotgun was first made in the year 1911.
That would depend on the type of barrel with the shotgun(plain,matte solid rib,or vent rib barrel)if a poly choke is present on the end of the barrel,and what condition the shotgun is in.