I'm not sure there's much I can add. They appear to be blank pieces of paper printed for use by the Frankfurt office of the NSDAP's Reichsleitung Amt für Lotteriewesen (Nazi Party's Government Office of the Lottery). The lottery office was a department of the Reich's Treasury, and it was responsible for running the numerous state lotteries.
Zeta Mattpost is a line of stationery paper. It's
still manufactured today by Zanders.