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.
Impossible to answer without the serial number
1924
It was made in 1919.
1905
about 1925
Impossible to answer without the serial number
612
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.
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.