i wonder how he could have a working/employment book of German Reich when he was born 1931? he was then 13 years old when it was May 1945 when WW2 ended. and then also Deutsches Reich did not longer exist. a 13 years old had to go to school if it was possible at the last time of War and not to work. he would have been normally in his last or next to last school-year that time.
are you sure it is HIS book? his birthdate to find there?
can you make a scan of it and make an attachment here, so we can read it?
or you send me in a private message if you will not state here.