The building that served as the exterior of Sue Lin's apartment is 834 Washington St., San Francisco, CA. It still stands as of this writing (04/2019) almost completely intact. There is a business on the ground floor, but the three floors above it remain, and nearly all the adornments remain. (It can be viewed on Google maps, street view.)
The Williams' apartment building is the Brocklebank, most famous for its appearance in Vértigo (1958). It still stands in 2022, with only a slight change in the entrance awning. (It can be viewed on Google Maps.)
The car driven by Walter Williams is a yellow 1948 Packard Victoria 8, the most luxurious and expensive convertible of its day and America's leading luxury make for several decades. Only 3,486 were made at an MSRP of $3,250 ($41,500 in 2023). In excellent condition, this car could be worth over $100,000.
Even though the movie is set in fictional Larkspur, ID, it actually was shot in Larkspur, CA. Downtown Larkspur can be seen in the town shot (at around 50 mins), and later scenes are set in nearby locations.
First film for Anna May Wong in seven years since Inconquistable (1942). It would be her penultimate film, her final one, Retrato en negro (1960), eleven years later.