No: 1743/ 62
Winkelfernrohr 6 x 20.
Possibly this instrument was manifactured by Carl Zeiss Jena in 1962. It was developed in WW 1, and was also used in WW2 . During the Cold War it was used by the NVA and other troops of the Warsaw treaty armies.
Such a periscope is very handy in trench and city warfare.
A tree screw is attached.