Copy of Huckleberry Finn by Samuel L. Clemens pricing?

A friend of mine has an ancient copy of Huckleberry Fin but instead of the Author being listed as Mark Twain, it is listed as Samuel L. Clemens. The book itself is in decent condition for it's age, a few torn pages and a semi-loose binding with a few dated gifting inscriptions in the front. We know it is worth a lot, but how much could we expect from it? Furthermore, where would she be able to sell it?