Speaking of Ithacas, IMO anyway, the only Ithaca side-by-side guns worth owning if you want to shoot modern 2&3/4" loads are the NID series- I looked up Ithaca double gun values in my 2014 edition of the Blue Book- for reasons which I can't quite fathom- a Flues No. 2 grade 12 gauge and a NID No. 2 12 gauge are considered to have the same retail values, condition being equal between the two Ithaca models-
The later versions of the Nitro Special are all 2 3/4" guns, have a few of the same features as the NID, and are more than up to the task. They cost less than the NIDs, or Flues, for what that is worth.
Best,
Ted