The name R.DANNHÄUSER probably indicates the advertising/design company Click for cover's details The company is usually involved in covers advertising various businesses ( Click for cover's details), it is possible that the cover frame was simply taken from another venture, or the company was also responsible for the design of this cover.
PASSAVANT is a name used by the manufacturer ACO. To specify products related to drainage systems.
Photographer’s note: At least two manhole covers laying before the St. Reinoldus church, Dormunds main church, features a view of the very church as it likely was before 1943.
Translation of the text on the cover: CITY OF DORTMUND