From your description the gun you have is the "New Double Bolted Gun" In 1915 Ithaca replaced the New Ithaca Gun with a model referred to as "our new model two bolt hamemer gun The new hammergun had coil springs powering the external hammers. The "two bolt" lock up was accomplished by a bottom bolt and y the top lever engagement with the rear nug of thrib extension. Lower grade models were marfked on both sides of the frame with a setter dog and the logo Ithaca Gun Co.
My 1999 standard cataglog of firearms pricing indicates values from $1,100.00 to $100.00 in poor condition. If you have the ability and tools to restock it it may not be much money involved. HOwever, to have it done the cost would outweigh the value of the gun. (Opinion) I don't know if I would do the refinish on the iron. Barrels especially.