That nickname was actually used for NBC, not CBS.
The nickname came about in the 1950s due to a few factors:
* High-quality programming: NBC boasted high-quality shows like "The Today Show," "The Tonight Show," and "The Hallmark Hall of Fame."
* Sophisticated audience: These shows attracted a more sophisticated and affluent audience, much like the clientele of the upscale jewelry store Tiffany & Co.
* Advertising: NBC's advertisers were also upscale, further reinforcing the association with Tiffany's.
So, while CBS has never been called the "Tiffany Network," the nickname is firmly associated with NBC for its history of high-quality programming and sophisticated audience.