If you listen carefully to a clear transcription, you can (very rarely) hear the script paper fall to the ground, which is what most radio actors did as the show progressed instead of move the paper to the back–the fact that papers aren’t on the ground suggests that either this was the beginning of the show, or it was a staged shot for promotional purposes. Often, you’d have more than one microphone for actors to use. The Shadow used 3 microphones for its show. I have a book on producing radio shows which has a diagram of the Shadow studio. I’ll have to pull the book out of storage to take a photo of that page sometime.
Each script page had about 1 minute of audio typed on it. Usually a show would be about 25 minutes long, giving 5 minutes of time for station breaks and commercials, unless the show was “sustained,” meaning that it was bankrolled by the network instead of an advertiser. As television gained in popularity, many shows were sustained.
The end of the golden age of old-time radio was 1962, when Suspense and Yours Truly, Johnny Dollar broadcast their last shows. However, 12 years later, Himan Brown would convince CBS to broadcast an anthology series called the CBS Mystery Theater, which broadcast weeknights from 1974 until 1982.
(More: Gangbusters– Archived Episodes.)