From John Barry.org.uk
United States - 1970
Director - William A. Fraker
Starring - Lee Marvin, Jeanne Moreau, and Jack Palance
Vertical format poster from Movieposter.com
Japanese poster from Movie Poster Posters.
These are just the best of the images for this film, you can see more at MovieGoods.
Also, in 2003 a sequel was made starring Tom Selleck as Monte Walsh.