Ironside's office/apartment was on the fourth floor of the Old San Francisco Hall of Justice. Stock footage of the building appeared on many episodes for the entire series run (1967-1974). The building itself was abandoned in 1961 and demolished in 1968.
Since he was a police detective, the van he used would have been his official police vehicle. As such, the license plate should have had an "E" exempt plate. However, it only had a standard California blue plate with 6 gold alpha-numeric characters.