I did a quick search on ABE and only found this book which has red covers not green. I presume this is a later reprint ... it only had a value of $25.
Harper and Brothers, 1899. Book Condition: Very Good. red cloth covers. faded spine cloth
The bookseller's name is Ronald Purmont of Newport, NH. You could e-mail him. He may be a Mark Twain collector and know more about your book.
I also went to abaa.org and entered the name of the book and found 12 copies for sale. There were also a few pictures of the book that you can compare your copy against.
