Not currently produced. Start with your local gun shop.
You have a Lewis or NIG model, built in 1903.
Forearm iron and watertable are the easiest places to obtain this info
$800 to $1000 depending on the condition.
If this is an old side by side it would be a Baker model made in 1886. Serial numbers of Ithaca shotguns for that year were 2448 - 4101.
Made in 1925
I have an Ithaca model 100 shotgun . It appraised for $700.
I would say that you have a Ithaca model flues double barrel shotgun that was made in the year 1923,with the serial number that you provided.
The Ithaca side by side 12 gauge serial 188650 was made in 1927.
If the shotgun is a hammerless double, it is a Baker Model produced in 1899 (per Dixie Gun Works, Ithaca Serialization Guide) That serial should be a 1926 production NID. sales@countrygunsmith.net
That should be a "New Ithaca Double", and if it is in very good condition is probably worth around $500-$600. Monitor www.gunbroker.com to see what comparables are going for now.
The gauge is stamped on the water table by the serial number. It is a Flues model made in 1924.
Try here - http://www.ithacagun.com/e -