The First "Radio Station" Copies

Barring transcriptions, V-Discs, and "demonstration copies" (example: the "Whirl-Away 45"), what label released the first discs specifically marked "Radio Sation Copy"? The earliest one I have is a Spike Jones disc from 1947 or '48 but I know there has to be something earlier than this.

There is not in actuality. 1947-1948 is when record companies began courting radio stations for airplay. If I recall correctly, MGM was the first label to court disc jockeys.