The four-digit postal codes are the official ones specified in the directory of towns and cities: https://www.cadastre.ch/de/services/service/plz.html Institutional postal codes that are not listed in the list of localities have been assigned to a postal code with spatial reference (e.g. 3000 Bern 65 to 3014 Bern). An assignment to the municipalities is possible using the Federal Statistical Office’s GWR correspondence table between postal code and municipality: https://www.bfs.admin.ch/bfs/de/home/grundlagen/agvch/gwr-korrespondenztabelle.html