If you cannot easily see a serial number, then it was manufactured prior to 1968 and doesn't have one.
Your Winchester shotgun was manufactured in 1914.
It was made in 1947
No published sn data
Your shotgun was manufactured in 1947.
You cannot the serial number is required.
1956 This shotgun WA manufactured in 1956
It was manufactured in the year 1920.
No way to answer without knowing the model.