The now-iconic CBS "eyemark" logo, designed by William Golden, was first introduced on October 20, 1951. Since its introduction, the eye design itself has remained unchanged, but the type style for the network's wordmark has been changed frequently. Sometimes the type style has been changed on a yearly basis, and it is not unusual for CBS to use several variants of it at once.
The wordmark was placed inside the eye in 1951.
The wordmark was placed back inside the eye in 1959, but had a different font.