There is not enough information to set a value. Is it still working? How old is it? Who made it? What model is it? What condition is it in? Without this information no estimate of value can be...
it depends on what brand it is a mossberg or Remington shouldn't be more than $450 but if its made for skiit or trap shooting it would be at the most 2,500
If you go to www.gunbrooker.com you can see what owners of old Ithacas are asking for their guns. Having seen a number of NID and Fluues models at gun shows they most often go for $300 for a rougher...