It should be on the under side of the receiver in front of the trigger guard and the loading port. it would be a number 7 digit's long, if it's a newer gun it may start with a letter.
Your serial number indicates that your Winchester model 1912 shotgun was made in the year 1920.
With the serial number that you supplied,your Winchester model 1912 pump action shotgun was made in the year 1916.
your model 1912 Winchester shotgun was made in 1918.
with the serial number that you provided,your winchester model 1912 shotgun was made by winchester in 1930.
Your Winchester model 1912 pump action shotgun was made in 1916 with the serial number that you provided.
Your Winchester model 1894 was produced by Winchester in 1912.
Your Winchester model 1912 pump action shotgun was made in 1917 with the serial number that you provided.
With the serial number that you supplied,your Winchester model 1912,pump action shotgun was made in 1961.
With the serial number you provided,your Winchester model 1912 shotgun was produced in the year 1954.
With the serial number provided,your Winchester model 1912 shotgun was made in the year 1957.
1919
1919