When C.C. first gets home at the beginning of the movie, the doctor's wife wonders at the noise - may be he had burglars. C.C. replies, " Don't worry, I don't have anything worth stealing." And immediately we see TWO gorgeous Art glass lamps, definitely Tiffany and probably worth about $15,000 now. At the time this movie was made 'art nouveau' was considered a joke on the antique market.
The two Tiffany shades (the patterns are Daffodil and Spider) actually sell for between $20,000 and $40,000 apiece in today's market. In addition, the apartment decor features a Periwinkle shade (made by the Unique Art Glass and Metal Company) worth between $1,500 and $2,000 at present.
From the 1930s through the mid 1960s, leaded glass shades were so out of fashion, so unpopular, that they were the sort of thing that you'd find in thrift shops. So, during those decades set designers used leaded glass shades to indicate a dwelling was poor or lower class (or at the very most, lower middle class).
It's an interesting detail to watch for... I've seen the same Duffner and Kimberly "Owl" shade used in half-a-dozen MGM films from the 1930s through the 1950s. And in every single case, the shade was used in the home of a character who didn't have much money.
Yep, it's fun to watch for these things! For instance---Judy Garland's brass bed from "Meet Me in St Louis" also appears in Ingrid Bergman's "Gaslight." (Though, this is a very easy one to spot, since the bed is so distinctive---the brass is curved into swan necks.) And the same stained glass shade appears in two Hitchcock pictures: "The Man Who Knew Too Much" and "The Trouble with Harry," etc., etc.....