Original leather book or journal cover. It has a cloth loop and a thin pocket to capture one side of a book cover. Inside, it is property stamped to the DAF Deutsche Arbeitsfront which is the largest labor union* in history. I am not sure if this was for a specific book or just for some official notebook. Pictured with a book inside to show how it might have been used (book not included).
*Depending on what you consider to be a labor union. It can be debated whether or not the DAF can be considered a true labor union, even though that was effectively the role it played and what it replaced, although it was functionally rather different.