It is a common practice for films shot in the Academy ratio (1 to 1:85) to be filmed using standard 35mm film (ratio of 1 to 1.37) and then masked to 1 to 1.85 either in the camera or in the projector. Sometimes the films are not masked in camera because the filmmakers intend to show the entire frame on television. This was done "The Princess Bride" and many other "open matte" films. (For scope films (1 to 2.35) this same thing can be done with Super 35 MM film). For these films, the letterboxed version actually contains less image than the full-screen version. This is the case with Touch of Evil. [On "Lolita" and "Dr. Strangelove," Kubrick sometimes masked the shots and sometimes didn't, and he preferred that the video versions match the negative. Thus, the approved video versions of these films have aspect ratios that vary from shot to shot.]
I've seen a a few films where the projectionist did not properly crop the movie. Sometimes the shape of the screen is incorrect, and sometimes the projectionist has not aligned the frame correctly -- so for example, part of the bottom that should cropped is instead visible and much of the top of the frame that should be visible is cropped.