It may have been a matte painting. The filming locations page only lists the house exterior and a studio.
1933 was way before background digitalization so that's probably not the answer.
No two persons ever watch the same movie.
jonkennedy — 9 years ago(January 28, 2017 06:09 AM)
It was not a matte painting as the background through the office windows was not still. It was a rear projection of some unknown real factory somewhere.