For all Habsburg historians out there: in my last two years of research I learned that both the police archives in Vienna and Milan have been effectively destroyed. In Vienna the police archive (Polizeihofstelle) burned down in 1927 due to the Justizpalastbrand. And Milan was heavily bombed by the allies in 1943. The Archivio di Stato in Milan contains literally nothing of interest in terms of policing anymore. And most of the Polizeihofstelle files are either destroyed or badly burned. The archivists in the Österreichische Staatsarchiv are unable to tell the state of these files until you request a box and they can look inside (if it exists).