What is the value of a first edition copy of The Adventures of Tom Sawyer 1876 publisher Saalfield Company?

I don't believe the Saalfield company was started until 1900, and I believe the original publisher was American Publishing Company. Although, I believe it was published first in Brittan by Chatto and Windus due to due to copyright difficulties. However, it is possible my research is wrong, so verify for yourself as well.