1938 Calendar / Day Planner with Feldpost Nr.
1938 calendar / day planner made by Heinrich Mittag Magdeburg und Hannover. It has a feldpostnummer written in it, so the owner was in the military, but he virtually never used the planner. I only found one entry.
It also has a lot of useful information inside: street signs, license plate identification (including Wehrmacht and SS), currency exchange info, etc. For a basically unused day planner, it is very interesting to look through.
It measures about 5 5/8" by 3 3/4".