You can't. You can find the serial number and from that you can get a ballpark figure on date of manufacturer
your Winchester model 12 shotgun was made by Winchester in 1959.
your Winchester model 12 shotgun was made in 1940.
Your winchester model 1897 shotgun was made by winchester in 1908.
your model 12 Winchester shotgun was made in late 1959.
1914
year 1939
1939
1961
With the serial number that you provided,your Winchester model 1912 pump action shotgun was made in the year 1941.
your Winchester model 12 shotgun was produced in 1915.
Your serial number indicates that your Winchester model 1897 pump action shotgun was made in the year 1942.
date of manufacture is 1915