Hercules brand is made by Iver-Johnson first introduced in 1900 and has many replicas but not worth too much about $100.00
Serial numbers were not required on rifles and shotguns until 1968.
With the serial number that you provided,your Ithaca double barrel shotgun with the damascus barrels was produced in the year 1900.
Check the barrel and receiver
No sn data published
Check the receiver and barrel
look on the breach, barrel.
Try the receiver, barrel, forend
If there is a serial number, it should be conspicously marked on the receiver. Shotguns and small caliber rifles did not require serial numbers before 1968, so many do not have one. If it is a break-action single shot or double barrel, there may be additional markings on the bottom of the barrel(s) and on the flat parts of the action that the barrel covers when the it is closed. The Hercules brand name was used by Montgomery Ward on guns made by Iver Johnson and J. Stevens.
You may have to break the shotgun down in to the barrel section and the receiver section first.Look under the barrel section on the flat just ahead of the lug for the serial number.
No published sn data