I had the chance to saw it in the Cinemateca Nacional a few years ago, but I missed, I know its a very uncommon film, with Glauber Rocha in it.
That's one I been wanting to see for a long time but never got the chance to, I'm not a big fan of Godard's Cinema, but i Know his importance. It's funny how this left wing directors, (Ferreri also did it) use the western genre to pass their message, westerns were really to most important film genre in Europe at the time.
P.S. There's also another film with the same name was directed by Roberto Enrico and had Malcom Macdowell on it by the way is a very good film. and a very political one too