screengrabs
From the NY Times dvd review:
I don't doubt that some projectionist went ahead and slapped a 1.85 projection lens on this for revival, but I have it on dvd, have a tv broadcast tape, and have seen it in the cinema and in each instance this film, projected 1.33, exhibits some of the most perfect 1.33 images in the whole history of the cinema. Alton was truly the master of fullscreen. The style is identical to that employed in his work with Mann (RAW DEAL, TMEN, THE BLACK BOOK, as well as HE WALKED BY NIGHT), as well as lesser known gems with other directors i e THE AMAZING MR X.This Image Entertainment DVD release of The Big Combo shows that this definitive 1950s film noir still packs a wallop. The clean source print used has been released in its original full-screen aspect ratio and shows off John Alton's groundbreaking black-and-white cinematography to excellent advantage. Alton's work here is so powerful that it has tended to overshadow Joseph H. Lewis' expert direction. While Lewis only made a handful of really good movies, The Big Combo ranks up there with Gun Crazy and My Name Is Julia Ross as the best in the noir cannon. The list price on this DVD is high considering there aren't any extras to speak of.
There's a chance I could be wrong of course but I... doubt it.