This thin periscope was used as a replacement set for the larger observation periscopes. It was also used in the “Kleinstglocke” which have a central opening, such as the 486P2 and the 749P3 series. We also think that these periscopes have been used in the Czech Mg-cupolas.
Here is a “4” in the original box.
Here is a set of two, one has an extra extension tube.