It was made in 1919.
If you are referring to an old double barrel, it was made in 1919.
Your serial number indicates that your Ithaca shotgun was made in the year 1920.
It sounds as if you have a Ithaca Crass model shotgun,that was produced in the year 1903 by your serial number.
1924
Impossible to answer without the serial number
612
Impossible to answer without the serial number
1905
about 1925
5 years
With the serial number that you provided,your Ithaca double barrel shotgun with the damascus barrels was produced in the year 1900.
A model 37 with the serial # 10464 was produced in 1939.