My best guess so far for the text of the body of the letter is:
In Neu en der Facni he des vor florben en Generals Kurt v. Schleicher ich veu de wich hiermit on Ihre Firma wit over Bi Ae uw geft. Luseudeing aller enöglichen Biloces des Obernähuten Generals. welche sich im Besitz Ihres Firmer befinden. Die Rechusing miral neuge heu or besshat herolen.
Hoch achtungs voll
However, because I don't know German I'm sure this has some laughable errors. Could someone look this over and tell me if I'm on the right track? Actual translation help would be welcome too.
Here's a scan of the letter.
EDIT: Translated! And I've found another mystery piece of paper. One side's in German, I'm not sure what the other side is in (it looked kind of like Cyrillic to me but it's the old German cursive). There's a newspaper clipping attached to it that's piqued my curiosity.
Side 1: Mystery language?
Side 2: German