And the confusion continues...
Still playing around with the JVC player, I rented out the Criterion DVD of Fritz Lang's M, which appears to be at an aspect ratio of about 1.24, with windowbox bars on the sides instead of the top and bottom. It also has a translucent line running across near the top of the frame, like the DVDs of Cabinet of Dr Caligari. I wonder if this was some kind of signal to the projectionist to frame the picture on the screen at that point. Whatever the reason, it's an annoying distraction.
Also looked at the DVDs for KANE and LADY FROM SHANGHAI. With windowboxing, one can see that Welles sometimes windowboxed the frame himself! In KANE's montage of Susan's operatic tour (just before she attempts suicide), the frame has been windowboxed by Welles in order to express Susan's claustrophobic domination by Kane. Likewise, the funhouse sequence in LADY was windowboxed by Welles probably to express Michael O'Hara's sense of entrapment. It sure makes a big difference when you can see each image exactly as Welles shot it.

