The Altec 639. Originally the Western Electric 639, this microphone
enjoyed a long life even after the Federal government-mandated breakup
of Western Electric in 1947 (Altec was the pro-audio spinoff).
This particular speciman, mounted on a custom lucite base, was originally
used by CBS Television in Los Angles. Both a ribbon and dynamic element
were incorporated into the design. A switch on the rear of the microphone
selected either ribbon, dynamic, or a combination of both as the
active pickup elements.
The 639 was nicknamed the "birdcage mic" because
of its resemblence to a birdcage.