This rare piece is a pack of Kodak Verichrome Pan 4"x5" (10x12cm) film. the number 523 indicated that is was a pack of 12 shots to fit a pack adapter for 4x5 cameras, often used by press photographers as it was faster and easier than changing individual film holders on assignment.  The film was on a thin base that made it very flexible, as when you pulled the tab to "advance" the film, it looped it around to the back of the film pack, exposing a fresh sheet of film. Care was to be exercised in processing and printing these negative due to the thin, flexible (floppy) base, but it was very popular in its day and really standard for many photographers.  This really is a collectible but if you have the gear and want to try using it, up to you.  Please note the "develop by August 1945" label and the"Help the war effort" ask on the front of the package to return the metal case to the dealer to be returned to Kodak for re-use. Ships via USPS Ground Advantage.