The building called 'rigsregistraturen' is in fact the at that time just recently finished Herlev County Hospital - and obviously, it is then not located in Lundtofte either as said in the movie. There is no such institution as 'rigsregistraturen', where all information is stored, in Denmark.
The clerks in the basement of 'rigsregistraturen' go by the names of Monberg, Thorsen and Hoffman. 'Monberg og Thorsen' and 'H. Hoffmann og sonner' were two of the largest civil engineering companies in Denmark at the time.
The reliefs under the clock in the movie portray the faces of the creators of Olsenbanden, Erik Balling and Henning Bahs.
The clock of Copenhagen City Hall was rebuilt on the premises of Nordisk Film in Valby. For some shots it was moved into a horizontal position. The real clock of the City Hall is actually smaller than the one seen in the film.