There's a list of serial numbers by year at http://ithacagunrepair.com/page5/page23/
NID with serial # 446018 was made in 1927
serial #
Your serial number indicates that you have a Ithaca crass model double,that was made in 1903.
1906
It sounds to me that you have a Ithaca Flues model double barrel shotgun.With the serial number that you provided,your shotgun was made by Ithaca in 1917.
The serial number indicates Ithaca manufactured your Model 37 in 1956.
Ithaca Gun Company of Ithaca, New York was the manufacturer. "Flues" refers to the designer. These double barrel, two-trigger, side-by-side shotguns were made from 1908 - 1926. Check out http://ithacagunrepair.com/page5/page23/ for a list of serial numbers by year of manufacture.
Its an Ithaca Flues model made in 1921
With the serial number that you provided,your Ithaca double barrel shotgun with the damascus barrels was produced in the year 1900.
Date of Mfg. is 1947
1949
By your description,it sounds as if you have a Ithaca model Flues double barrel shotgun that with that serial number was produced in the year 1914.